1Mrs. Anne Berkeley writes in a letter to her son, “had he [George Berkeley] built as he has pulled down, he had been a master builder indeed; but unto every man his work: some must remove rubbish, the others lay foundations.”  Perhaps she wants something like the view on angels in § 81 of the Principles?  Colin Turbayne takes this to mean the Bishop’s persistent interest in getting rid of the myth of the mechanism and its explanatory potential. He demolished other theories as well, such as materialism, scepticism, and the possibility of abstract ideas. But he constructed too. He built his own world of ideas; yet it is true that his constructions are sketchy. And they did not sell well, if we compare their success with some of the key ideas of Newton, Locke, and Descartes.
2Somehow such speculations miss the point. Berkeley practiced destructive criticism when he was young, but during his long and isolated years in Cloyne he changed his approach. Siris (1744) is a constructive work.  He wanted to lay foundations and be a master builder. I find it amazing that Mrs. Berkeley dismisses it, especially because Siris was a popular and successful book in its own time. We can say that the neglect of Siris started early; it was an ill-fated book even when it was still a commercial success. Yet it is an important book.
3Siris contains a constructive theory, even if it criticizes mechanistic explanations and many other things. Its author wants to build a chain from lower to higher things, starting from pine tar and extending to God as a Trinity. He goes from the questions of human health and medicine to the problems of theology. Not much of what he has to say is original as such but his total project and its outlook is novel anyway. He develops a grand theory of health, life, the world, and God which are supposed to show all these varied things as essentially connected, that is as a plurality in unity. It is difficult to say how well he succeeds but anyway he tries his best.
4My opinion is that he succeeds much better than those who have read Siris only casually may be ready to admit. The point is that Siris has its foundational aspect which deserves our respect, once we detect and see it. The key to successful reading of Siris is to recognize, tolerate, and utilize its ambiguity. Berkeley wants to construct a bridge between science and religion, but in his own time it is already too late to do so, except by means of the ambiguation of the borders between science and religion. He does it in his metaphysics. In this paper I try to show how he does it.
5I concentrate on the final theological sections of Siris where the Bishop discusses the Holy Trinity and some possible metaphysical models of its interpretation. I hope also to throw some light on one of the most important question concerning Siris, namely the ambiguous character of light, fire, and spirit as causal instruments in the hands of God (or, light/fire/spirit because all three are basically the one and the same substance).
6Light is, according to Sir Isaac Newton, a shower of small material particles coming from a source of light.  As an enlightened man of science Berkeley accepts this physicalistic theory, but he says also that light is God’s messenger and an active principle.  Berkeley writes: “It should seem that the forms, souls, or principles of vegetable life subsist in the light or solar emanation […], which in respect of the macrocosm is what the animal spirit is to the microcosm –the interior tegument, the subtle instrument and vehicle of power” (§ 43), and “light or fire might indeed constitute the animal spirit or immediate vehicle of the soul” (§ 205). The soul and its causal effects are carried along by animal spirits which are light and fire particles. Most readers of Siris have said, however, that we should stick to the first scientific and instrumental view and treat the second metaphysical view as an ancient allegory and a figment of imagination.  In Siris, however, Berkeley talks about light and fire in two different senses, physicalistic and metaphysical. Light is as well matter as it is a vehicle of the soul and God. Light brings about changes in the world according to the will of man and God.
7Light is an ambiguous entity. It is a hail of small corpuscles from the Sun (according to physics), but notice what kinds of things subsist in light: forms, souls, and principles (according to metaphysics).
8This is a difficult thesis to understand and accept. The reason seems to be the modern reader’s inability to think in terms of traditional metaphysical and theological terms. The Newtonian idea of material light sounds so convincing; the metaphysical view looks, on the contrary, strange and implausible, almost meaningless. It seems that Berkeley himself struggles with this hermeneutical problem. He uses his ancient sources extensively in order to make sense of his own hazy intuitions although he never seems to be able to commit himself to their views. Yet, the Ancients indicate the right path.
9The following quotation shows how deeply ambiguous Berkeley’s text is: “Thus much it consists with piety to say, that a divine Agent doth by His virtue permeate and govern the elementary fire or light […], which serves as an animal spirit to enliven and actuate the whole mass, and all the members of this visible world. Nor is this doctrine less philosophical than pious. We see all nature alive or in motion. We see water turned into air, and air rarefied and made elastic […] by the attraction of another medium, more pure indeed, more subtle, and more volatile, than air. But still, as this is a moveable, extended, and consequently a corporeal being […], it cannot be itself the principle of motion, but leads us naturally and necessarily to an incorporeal spirit or agent. We are conscious that a spirit can begin, alter, or determine motion; but nothing of this appears in body. Nay, the contrary is evident, both to experiment and reflection” (§ 291).
10First he says that God “permeates […] the elementary fire” and this implicates that light/fire contains “the principle of motion”; then he says that light/fire is “corporeal being” –which cannot be or contain the principle of motion. Does this mean that God permeates the physical world or just the corporeal light particles? But Berkeley is a theist who must keep God and the world separated in a normal dualistic manner. He says that all nature is alive, but seems to mean that this is the same as saying that all nature is in perpetual motion. In the end of the quotation he takes back his first suggestion, namely, that God somehow permeates matter. An attentive reader is left baffled. The difficult point is this: If the principle of motion, God, permeates matter, matter seems then to contain the principle of motion. This is an implausible view if light/fire is a set of corpuscles in motion.
As I said above, the real ambiguity is between metaphysics or theology and empirical natural science. In other words, for a pious person God is indeed present in light but to a natural scientist light is just another corporeal entity. This is the reason why we need to read the theory of light metaphysically and theologically. To do so we start from the last pages of Siris.
My methodological suggestion is that we treat Siris as a chain of arguments, which it is, and read the chain in a descending order. Siris was of course written in an ascending order, from low to lofty themes. But when we begin from the high end, we can see better what light/fire/spirit is and why it is such an ambiguous notion. My point is that when we start from the low end of the chain, light is material bullets from the Sun; when approached from the high end via God and the Trinity, it is something else. Berkeley did not want to write another book of scientific criticism. He really wanted to construct a new metaphysical view of the world. And this is the consequence: my reading gives us two sets of different results. Taken together these reveal the ultimate truth. Light/fire/spirit is not only a material thing; it is also a metaphysical principle, or a Platonic metaphysical form, which then hints at theology.
11Siris, as its name indicates, is designed as a chain of arguments which start from tar and tar water and extend all the way to God.  Such a chain is a causal chain because it is created and maintained by God, who is pure activity and the primary causal agent. In this sense Siris is a comprehensive treatise, even if it is a slim volume, which deals with the world and whatever is there. The structure of the text of Siris is analogous to the structure of the world –this is the key point which should be kept in mind. Siris has something to say about theology and God.
two possible descending chains:
13In chain one tar is a natural element of macrocosm, if we think in terms of natural science. But tar is also medicine in chain two which contains the principles of health and vitality, and as such it does not belong only to the realm of science. It is somehow divine. Tar is also an ambiguous entity because it belongs to both chains.
The argumentative outlook of Siris is dependent throughout on such ambiguities. Everything is ambiguous because, as an object of thought, it is at the same time an element of science but also metaphysically dependent on God. Therefore no such thing as one unified and conceptually fixed world exists. It all depends on whether we read the chains of Siris in ascending or descending order –as I will try to show below.
My point is, however, that Siris is a chain of chains which can and should be made visible; even if it remains as a tentative effort. It is a mistake to think that a single ascending chain starts from tar. Berkeley may give such an impression by means of the subtitle of Siris, “a chain of philosophical reflexions and inquiries.”
14On top of the chain Berkeley mentions the Holy Trinity, or Farther, Son, and the Holy Ghost which he correlates with other trinities like light/fire/spirit. This is nothing new. In Renaissance Platonism such identifications were commonplace. The author of Siris has not invented anything new. On the contrary he just picks his own favorite identifications and utilizes them.
15Berkeley writes in the end of Siris (§ 362) as follows (this is one of the key quotations from my point of view): “In the administration of all things, there is authority to establish, law to direct, and justice to execute. There is first the source of all perfection, or Fons Deitatis; secondly, the supreme reason, order, or logos; and lastly, the spirit, which quickens and inspires. We are sprung from the Father, irradiated or enlightened by the Son, and moved by the Spirit. Certainly, that there is Father, Son, and Spirit; that these bear analogy to the sun, light, and heat; and are otherwise expressed by the terms Principle, Mind, and Soul, by One or to en, Intellect, and Life, by Good, Word, and Love; and that generation was not attributed to the second Hypostasis, the nous or logos, in respect of time […], but only in respect of origin and order, as an eternal necessary emanation; these are the express tenets of Platonists, Pythagoreans, Egyptians, and Chaldeans.” This is Berkeley’s summary of certain theological traditions, both Christian and pagan. He offers no evidence to support such identification. He refers merely to what has been said. Everything must be taken by faith. For this reason alone we have left philosophical metaphysics behind and moved over to theological speculations. We have reached the limit of all philosophy. Berkeley invites us to think and speculate theologically with him.
16The Holy Trinity is said to be analogous to many other threefold entities. The main problem is, however, that Siris introduces first light/fire/spirit as the main instrument of God, but when Berkeley moves over to theology he more or less forgets it. One would expect that light/fire/spirit correspond with Father/Son/Spirit, but the case is more complicated. We find Berkeley mentioning light and spirit but not fire. Light is fire as experiments with a magnifying glass show (Siris, § 158). Instead Berkeley speaks now of heat which of course may be the same as fire. Notice that when we compare columns 1 and 2 below, illumination and light correspond just as movement and heat do.
A possible way of summarizing such a crucial and fantastically complicated paragraph is given by means of my table below. We find eight trinities:
17Berkeley continues in the end of Siris where he discusses Plato and Platonism as follows: “And, indeed, what this philosopher in his Phædrus speaketh of the super-celestial region, and the Divinity resident therein, is of a strain not to be relished or comprehended by vulgar minds; to wit, essence really existent, object of intellect alone, without colour, without figure, without any tangible quality. He might very justly conceive that such a description must seem ridiculous to sensual men” (Siris, § 366). This is his grand vision expressed with perfect style and unforgettable beauty. What is real is abstract for a sensual man.
18Berkeley seems to condemn his own early criticism of abstract ideas and even his immaterialism. He used to be one of the “sensual men.” Now a world beyond sensual ideas emerges, not the vulgar world of matter and materialism, but a full-fledged metaphysical world, that of existent essences and intelligible objects –“without color, without figure, without any tangible quality,” as he so beautifully puts it. In the end, the Bishop widens his philosophical perspectives so that he is able to comprehend the real world beyond perceptual ideas and natural science. He realizes that he has no clear vision or view of what there is, but, he says, he can understand that something foundational is needed and God provides it to those who are willing to search. The Ancient philosophers have made so much progress toward proper metaphysics that moderns should imitate them. Such an extension of the world must be accepted, according to Siris. The scientific account of the world can never be adequate alone.
19Next, let us apply the metaphysical view to light/fire/spirit which obviously is not just an object of scientific study. It is much more when seen in the light of metaphysics and theology. Let us discuss first the concept of a principle. By introducing it, Berkeley takes a step toward Platonism and its theory of forms. He says that God is the Principle. He also seems to say that light/fire is a principle. We know that in alchemical language salt, sulphur, and mercury were not just salt, sulphur, and quicksilver as concrete chemical substances but they were their respective principles. For instance, mercury is the principle of all metals, or the birth of them. This mercury is different from what we call quicksilver, which is a visible and tangible substance. 
20So what is a principle? One of the many meanings of a principle is, according to the Merriam-Webster dictionary, “an underlying faculty or endowment,” or ability. In everyday language we normally speak of practical principles as normative rules which guide and regulate our actions and programs. For instance we can say that it is the main principle of legislation that justice is done. But what do we mean when we say that light/fire is a principle, or that salt is a principle? What is the principle of light and fire? It is their essence and a Platonic idea (Siris, § 335).
21In Siris, principles are introduced via Wilhelm Homberg’s chemistry: “Mr. Homberg, the famous modern chemist, who brought that art to so great perfection, holds the substance of light or fire to be the true chemic principle sulphur […], and to extend itself throughout the whole universe. It is his opinion that this is the only active principle; that mixed with various things it formeth several sorts of natural productions, with salts making oil, with earth bitumen, with mercury metal; that this principle of sulphur, fire, or the substance of light, is in itself imperceptible (Siris, § 189).
22Homberg says that fire, substance of light, or the substance of light and fire is the only active principle in the universe and it is also the chemical principle of sulphur. If fire is the chemical principle of sulphur, this is to say that sulphur is “fiery.” Sulphur does what fire does. Notice also that Homberg talks about an “active principle” and Berkeley seems to accept this usage. 
23Berkeley explains what Homberg says without committing himself to his views. But when the reader reads on, he notices that he first refers to other modern chemists, then again to the ancient authorities, and finally he writes as if it were his own opinion: “But this active element [light/fire] is supposed to be everywhere, and always present, imparting different degrees of life, heat, and motion to the various animals, vegetables, and other natural productions, as well as to the elements themselves wherein they are produced and nourished” (Siris, § 190). If this were not the case, “the whole [world] would be one great stupid inanimate mass.”
24The conclusion is that light/fire is an active principle or an element which orders and animates the world in a causal fashion. Everything we see around us is ordered and made comprehensible by the light/fire which is God’s active instrument. This is a strange notion because one would expect Berkeley to say that anything that is an instrument is also in itself passive. But this is not what he says. God permeates light/fire and His activity is present in it. That is what he says.
25In metaphysics a principle seems to be, by definition, a functional essence, form, or idea which influences its own and suitably restricted realm. Hence a principle may constitute and causally influence the world. Think of light as a principle. The essence of light is to illuminate and make understandable in that realm where things can be understood, where everything is not mere darkness. Therefore, any measure which promotes perceptual or mental understanding follows the principle of light.
26If the functional essence of light is to illuminate, anything that illuminates follows the principle of light. The principle of light is exemplified in all illumination. What about the principle of spirit? Whatever animates a being follows its principle. When we see a flame or feel the heat, we know that the principle of material change is present. Berkeley thinks of the burning bush in the desert, which is divine fire as a miraculously visible entity. God is the Principle, and in the burning bush this primordial principle now appears as a flame (Siris, § 186). It is a miracle.
27In this way light, fire, and spirit stand for their own essential functions or principles whose effects we can observe everywhere. Whenever we see illumination, expansion, and motion, animation, life, and health, we may legitimately speak of light, fire, and spirit, respectively.
28Let us analyze some examples of Berkeley’s text in Siris: “The Stoics also taught that all substance was originally fire, and should return to fire; that an active subtle fire was diffused or expanded throughout the whole universe, the several parts whereof were produced, sustained, and held together, by its force. And it was the opinion of the Pythagoreans, as Lairds informs us, that heat or fire was the principle of life, animating the whole system, and penetrating all the elements” (Siris, § 166, my italics).
29Here Berkeley utilizes the Stoic view which he regards with great sympathy. Yet, it is impossible to say how much he actually accepts. But perhaps we need not even try because the mere fact that Berkeley quotes them is sufficient to show that he finds them important. The exact words do not matter. The partially hidden truth is important, and here we can see what that truth may look like, Berkeley seems to say. Anyway, fire is the principle of life and this fire, as animal spirit, animates all living things. Sometime it does so as fire, sometimes as animal spirits, always depending on the context.
30Next, a quotation follows: “There is no effect in nature great, marvellous, or terrible but proceeds from fire, that diffused and active principle, which, at the same time that it shakes the earth and heavens, will enter, divide, and dissolve the smallest, closest, and most compacted bodies. In remote cavities of the earth it remains quiet, till perhaps an accidental spark, from the collision of one stone against another, kindles an exhalation that gives birth to an earthquake or tempest which splits mountains or overturns cities. This same fire stands unseen in the focus of a burning glass, till subjects for it to act upon come in its way, when it is found to melt, calcine, or vitrify the hardest bodies” (§ 158, my italics).
As we see, fire does not only animate things, it also shakes them. Again, it is important to notice that fire is not visible culinary fire or a flame, but the principle of fire. Visible fire just exemplifies this great and noble principle. If it acts as the principle of fire dictates, it can be called a flame and fire in this empirical sense. Such is the reason why we call a flame fire: its essential effects or actions are of the correct kind.
Interestingly enough, Berkeley says that the burning glass focuses light and there “fire stands unseen.” Fire is first light, and when some flammable object enters the focus, light becomes heat and fire. This fluctuation of essences is understandable only if we think of light and fire under their special principles and not as particular substances.
31It is tempting to identify the Father with Fire, the Son with Light, and the Holy Spirit with (animal) Spirit –but Berkeley does not do so. Yet he comes close to saying so, for instance here: “The first Hypostasis contains all excellence and perfection, whereof it is the original source, and is eminenter, as the Schools speak, intellect and life, as well as goodness; while the second Hypostasis is essentially intellect, and, by participation, goodness and life; and the third, life essentially, and, by participation, goodness and intellect” (Siris, § 352).
32Here the Father is fire (fire is the origin of everything), the Son is light (light is intellect and illumination), and the Holy Spirit is animal spirits (animal spirits indicate animation and hence life) –such a reading may look plausible but it is not the only possibility.
33The main point, however, is that God, or the Holy Trinity, is repeatedly mentioned as the main active principle, a cause, or the Principle. The Father alone is mentioned as a principle in our table of trinities above, and I suppose this means an active principle. Only God is genuinely active, although finite spirits possess some activity as well. All of them are able to change the world around them by causal means according to their will.
34God as the Father is fire, but now the question is, how does God use light and fire as His secondary, instrumental cause to facilitate His free efficient causal agency? He has two separate playgrounds, microcosm and macrocosm. This distinction is very old. Equally old is the idea of the world (macrocosm) as an animal. When we think that God is a Trinity and a free causal principle, we should be able to understand how He governs everything by means of His instrumental causes which are light and fire, or the principles of light, fire, and spirit. We no longer discuss light as a Newtonian shower of small material particles. These little things can have no major active role in the world. All matter is passive of course.
35Anyway, the Father moves, the Son guides, and the Spirit animates the microcosm and the macrocosm. The Father exemplifies the principle of sun and fire, the Son that of light, and the Spirit that of heat. (See the table above, column 2.) And the Father himself is the Principle, or the rule, norm, and measure, on which everything depends. His functional essence is to rule over absolutely everything –this is His Principle. Thus anything or anybody that rules over something is divine due to the participation in this main Principle. Any King is divine under such a Principle. But then, in a classical manner, the Father, the Son, and the Spirit have their own principles which define their functional essences: fire, light, and heat. Such principles make the Father, the Son, and the Holy Spirit what they are. They are said by Berkeley to be One, just like his God is One. The three principles are one and the three divine aspects which constitute one God are one.
36Once we have come this far, we can try to understand how light and fire work as instrumental causes, when the corresponding Newtonian little light bullets need not be mentioned. My hypothesis is as follows: when something happens in a given causal context, it always happens under the principle of fire, light, or heat/spirit (motion, illumination, or animation). Therefore we can say that the cause of the change in question is fire, light, or heat/spirit –when we actually mean the corresponding principles. And those principles can be called active when they are mentioned together with God’s more or less direct influence. God as the Principle is active.
37Example: a big rock falls and smashes another rock. All motion is placed under the secondary principle of fire and the primary Principle the Father. Therefore, the Father did it by means of fire –this is what Berkeley says. We cannot see any fire here, of course because only the principle of fire is at work here. It is now easy to see what the explanatory ambiguity is like. In physical language, gravitational force makes the rock fall and the energy of its strike breaks the other rock.  For Berkeley this does not explain anything. He says that somehow light/fire explains the event. It is God’s will that the rock should fall, and He makes it fall. Here he uses fire as an instrumental or secondary cause. However, it is next to impossible to understand what this would mean. Does he send a hail of light-bullets from the sun to tear the rock loose and make it fall down? This does not make any sense. The rock falls even if it is dark. We see no fire. So, what explains the event?
38The Father is the Principle and all other metaphysical principles depend on Him, in the sense that whatever happens is explained by the Principle via the various principles which are subsumed under it. So, to say that God is active, or an efficient cause, is to say that in all events which take place in the world we see His influence, or all these events are examples of the application of His Principle. To explain an event in the world is to refer to Him because His Principle is exemplified in all change. And because this Principle is divided into three sub-principles, those of fire, light, and heat/spirit, all events exemplify one or more of them. All motion and change take place under the principle of fire as the Father; all intelligible events take place under the principle of light or the Son; and all phenomena of life are dependent on the principle of spirit or the Holy Spirit.
39This is the logic of Berkeley’s Platonic explanatory scheme. It does not matter how the various details are arranged. Many possibilities exist and the reader of Siris must make her or his own hermeneutical decisions. Yet it seems to me that the logic is as simple as it is impeccable, namely, whatever happens in the world exemplifies the principles of light/fire/spirit. Moreover, these principles are the sub-principles of the ultimate Principle. Therefore we can say that all events depend on and exemplify the Principle and, consequently, the three sub-principles. We can of course ask whether this explanatory scheme mentions efficient causes or formal causes, or both?
In his semi-physicalist language Berkeley describes the events of the world by saying that light/fire/spirit are God’s instruments and secondary causes (Siris, § 153-54). This can be said, if we read the chain of Siris in the ascending order. And as I said above, the problem is, how fire moves stones. We need to read Siris in a descending order, starting from the Trinity. There we find the necessary principles by means of which we can then explain, or at least understand, the world and its events. We find the principles of light, fire, and spirit. Whatever happens, happens because of these principles without which the world would be nothing but chaos. In the end Berkeley is a Platonist metaphysician and natural theologian. Light/fire may be corpuscular in nature but ultimately we are talking about their functional essences, principles, or forms which explain the world. These explanations are not immanently in the world but dependent on God who is outside of both macrocosm and microcosm.
Colin Turbayne, “Introduction to Berkeley’s Works on Vision” (Bobbs-Merrilll, Indianapolis, 1963), p. xii.
The Principles of Human Knowledge, in The Works of George Berkeley, vol. II, eds T. E. Jessop and A. A. Luce (London: Nelson, 1948).
Siris, in The Works of George Berkeley, vol. V, 1953.
Isaac Newton, Opticks (1730) (Amherst, ny: Promtheus Books, 2003). See also G. N. Cantor, Optics after Newton (Manchester: Manchester University Press, 1983), chap. III.
But see The Principles, § 27: active principles cannot be ideas.
T. Airaksinen, “The Path of Fire: The Meaning and Interpretation of Berkeley’s Siris,” in Stephen H. Daniel (ed.), New Interpretations of Berkeley’s Thought (Amherst, ny: Humanity Books, 2008), 261-281.
On tar and tar-water, see T. Airaksinen, “The Chain and the Animal: Idealism in Berkeley’s Siris,” in Stephen Gersh and Dermot Moran, Eriugena, Berkeley, and the Idealist Tradition (Notre Dame: Notre Dame University Press, 2006), 224-243.
See Lyndy Abraham, A Dictionary of Alchemical Imagery (Cambridge: Cambridge University Press, 1998), 124ff on Mercurius as the universal agent of transmutation.
On Homberg, see Luc Peterschmitt and Rémi Franckowiak, “La chimie de Homberg,” Early Science and Medicine, 10 (2005), 65-90.Online
See T. Airaksinen, “Berkeley and Newton on Gravity in Siris,” in Silvia Parigi (ed.), George Berkeley: Religion and Science in the Age of Enlightenment, in the International Archives of the History of Ideas (Berlin: Springer), forthcoming.