It has been a while since I've said anything about this weblog's namesake, so I've decided to remedy that by presenting the following three passages from Berkeley's Siris, my favorite Berkeleyan work. Siris gives us a chance to see a side of Berkeley that is often neglected; it enables us to see the Berkeley who thought that Stoic and Platonic metaphysics, however speculative, were worth taking seriously, and were probably on to something. (This side peeps into his better known works, the Principles and the Three Dialogues, as well as into the also-neglected Alciphron, but is easily missed. It could hardly be missed in Siris, however, where it comes out in full, and somewhat overwhelming, array.) In a reversal from the usual usage on this site, my comments are in italics.
1. The principles whereof a thing is compounded, the instrument used in its production, and the end for which it was intended, are all in vulgar use termed causes; though none of them be, strictly speaking, agent or efficient. There is not any proof that an extended corporeal or mechanical cause doth really and properly act; even motion itself being in truth a passion. Therefore, though we speak of this fiery substance as acting, yet it is to be understood only as a mean or instrument; which indeed is the case of all mechanical causes whatsoever. They are, nevertheless, sometimes termed agents and causes, although they are by nomeans active in a strict and proper signification. When therefore force, power, virtue,or action is mentioned as subsisting in an extended and corporeal or mechanical being, this is not to be taken in a true, genuine, and real, but only in a gross and popular sense, which sticks to appearances, and doth not analyze things to their first principles. In compilance with established language and the use of the world, we must employ the popular current phrase. But then in truth we ought to distinguish its meaning. It may suffice to have made this declaration once for all, in order to avoid mistakes. [Siris 155]
'Mechanical' here means roughly what we would call 'physical'. Berkeley's claim that motion is properly only a passion, something undergone, rather than a genuine action, is a common one in the period. The reference to 'this fiery substance' is a reference to what Berkeley has been discussing. Berkeley is much taken with the notion of a World Soul that is a 'pure aethereal fire'; and has been speculating (Siris is explicitly a speculative work, put forward not dogmatically but as food for thought) about its role in the functioning of the cosmos. This is part of the general drift of the work: from the properties of tar-water to the properties of mechanical causes to cosmic operations (the world soul) to minds to the divine mind to the Trinity. He has been treating the 'pure aethereal fire' (which he also calls 'light') as a cause, and is clarifying the sense in which he does not mean it.
2. The mind of man acts by an instrument necessarily. The το 'ηγεμονικον, or Mind presiding in the world, acts by an instrument freely. Without instrumental and second causes there could be no regular course of nature. And without a regular course, nature could never be understood; mankind must always be at a loss, not knowing what to expect, or how to govern themselves, or direct their actions for the obtaining of any end. Therefore in the government of the world physical agents, improperly so called, or mechanical, or second causes, or natural causes, or instrumetns, are necessary to assist, not the governor, but the governed. [Siris 160]
As we shall see in the next passage, there is more to this passage than meets the eye. The idea only hinted at here, that the laws of natures are rules we formulate to help us know what to expect, govern ourselves, and obtain our ends, is a key part of Berkeley's view of the laws of nature.
3. Mechanical laws of nature or motion direct us how to act and teach us what to expect. Where intellect presides there will be method and order, and therefore rules, which if not state and constant would cease to be rules. There is therefore a constancy in things, which is styled the Course of Nature (sect 160). All the phaenomena in nature are produced by motion. There appears an uniform working in things great and small, by attracting and repelling forces. But the particular laws of attraction and repulsion are various. Nor are we concerned at all about the forces, neither can we know or measure them otherwise than by their effects, that is to say, the motions; which motions only, and not the forces, are indeed in the bodies (sect. 155). Bodies are moved to or from each other, and this is performed according to different laws. The natural or mechanic philosopher endeavours to discover those laws by experiment and reasoning. But what is said of forces residing in bodies, whether attracting or repelling is to be regarded only as a mathematical hypothesis, and not as anything really existing in nature. [Siris 234]
As he goes on to note in section 235, this means that we can't suppose that there is any sort of real power in the particles composing bodies; so we come up here against Berkeley's occasionalism. Notice the emphasis again on the physical laws of nature being rules directing us with regard how to act and what to expect; on Berkeley's view, laws of nature are very closely analogous to grammatical rules. Like grammatical rules they are formulated after the fact, on the basis of the language they are interpreting; like grammatical rules they are pragmatically oriented, being primarily for use; like grammatical rules they are simply hypotheses that save the phenomena for practical purposes; and like grammatical rules we shouldn't take too seriously the fact that they posit something to exist. On the other hand, it must be understood that Berkeley is not, strictly speaking, an anti-realist about laws of nature, for he thinks there really are rules that constitute the 'course of nature': namely, the rules God uses in communicating to us the course of nature. This aspect of Berkeley's view goes back to some of his earliest thinking and is argued for in his first published work, the New Theory of Vision, when he argues that vision is, quite literally, a form of communication between the divine mind and the minds of creatures.