This hypothesis is very possible. For why should not God be able in the first instance to give to substance a nature or internal force capable of producing for it in an orderly way (as if it were an automaton, spiritual and formal, but free in the case of a substance which has a share of reason) everything that is going to happen to it, that is to say all the appearances and expressions it is going to have, and that without the assistance of any created thing? This is rendered all the more probable by the fact that the nature of substance necessarily requires and essentially involves a progress or change, without which it would have no force to act. And since it is the very nature of the soul to be representative of the universe in a very exact way (although with varying distinctness), the sequence of representations which the soul produces for itself will naturally correspond to the sequence of changes in the universe itself: while on the other hand the body has also been adjusted to the soul, in regard to the experiences in which the latter is conceived as acting outside itself. This is all the more reasonable in that bodies are only made for those minds which are capable of entering into society with God, and of celebrating His glory. Thus once we recognize the possibility of this hypothesis of agreements, we recognize also that it is the most reasonable one, and that it gives a wonderful idea of the harmony of the universe and of the perfection of the works of God.
There is in it this great advantage also, that instead of saying that we are free only in appearance and in a manner adequate for practice, as several ingenious men have held, we must rather say that we are determined in appearance only; and that in strict metaphysical language we are perfectly independent as regards the influence of all other created things. This again shows up in a marvellously clear light the immortality of our soul, and the ever uniform conservation of our individual self, which is perfectly well regulated of its own nature, and is beyond the reach of all accidents from outside, whatever the appearances to the contrary. No system has ever so clearly exhibited our exalted position. Since each mind is as it were a world apart, sufficient unto itself, independent of all other created things, including the infinite, expressing the universe, it is as lasting, as subsistent, and as absolute as the very universe of created things itself. We must therefore conclude that it must always play its part in the way most suited to contribute to the perfection of that society of all minds which constitutes their moral union in the City of God. Here, too, is a new and wonderfully clear proof of the existence of God. For this perfect agreement of all these substances, which have absolutely no communication with one another, could only come from the one common cause …
These considerations, metaphysical though they may appear, are yet wonderfully useful in physics, for establishing the laws of motion … For the truth is that in the shock of impact each body suffers only from its own elasticity, caused by the motion which is already in it … It is reasonable to attribute to bodies true motions, in accordance with the supposition which explains phenomena in the most intelligible way; and this way of speaking is in conformity with the notion of activity which we have just established.
Specimen Questions
1 Explain why Leibniz thought a purely mathematical account of nature was inadequate. What special features of reality does his theory of substance try to explain?
2 Why does Leibniz think that the ultimate constituents of nature cannot be physical, but must be metaphysical? Why on his view are ‘atoms of matter’ contrary to reason?
3 Leibniz argues that the soul is the principle of true unity or what is called the I in us, whilst the body is merely a unity in appearance. What are his reasons?
Suggestions for Further Reading (Including Internet Resources)
1 Leibniz, New System [1695], in Philosophical Writings, ed. G. H. R. Parkinson (rev. edn, London: Dent, 1973).
2 For other texts and commentaries on Leibniz, see readings at the end of Part I, extract 6.
3 A detailed study of the metaphysical aspects of Leibniz’s philosophy is R. M. Adams, Leibniz: Determinist, Theist, Idealist (New York: Oxford University Press, 1994). For an alternative reading of Leibniz’s metaphysics see D. Garber’s influential book, Leibniz: Body, Substance, Monad (Oxford: Oxford University Press, 2009).
4 The Stanford Encyclopedia of Philosophy provides an excellent entry on Leibniz’s philosophy of physics and his dynamics at https://plato.stanford.edu/entries/leibniz-physics/ (J. K. McDonough). See also the Internet Encyclopedia of Philosophy at https://www.iep.utm.edu/leib-met/
5 Further online sites with Leibniz texts, translations and relevant links are D. Rutherford’s at http://philosophyfaculty.ucsd.edu/faculty/rutherford/Leibniz/, and G. Brown’s at http://www.gwleibniz.com/.
Notes
* Gottfried Wilhelm Leibniz, New System of Nature and the Communication of Substances [Système nouveau de la nature et de la communication des substances, 1695]. Trans. G. H. R. Parkinson and M. Morris, in Leibniz, Philosophical Writings (London: Dent, 1973), pp. 115–25; with omissions.
1 1 Essay Concerning Human Understanding, Bk II, ch. xxiii, § 2.
2 2 Advocates of the traditional philosophy, based on Aristotle.
3 3 Leibniz refers to Descartes and his followers.
4 4 See Part IV, extract 4, below.
5 5 Nicolas Malebranche. See Part IV, extract 6, below.
6 6 The ‘deus ex machina’ was the god often lowered onto the stage at the end of Greek tragedies to sort out all the outstanding problems in the drama.
6 Nothing Outside the Mind: George Berkeley, Principles of Human Knowledge*
The debates in the early modern period over the ultimate nature of reality led in many different directions. Descartes, as we have seen (extract 3, above) regarded matter as inert, passive extension; and both he and Locke considered that our ideas of sensible properties (such as colours, tastes, smells) did not really inhere in, or belong to the physical world, but rather were effects produced in the mind alone. Reflection on these issues led the Irish philosopher George Berkeley to the radical conclusion that nothing at all could be said to exist outside the mind. In the following extract from the Principles of Human Knowledge (1710), he attacks the Lockean distinction between primary and secondary qualities (see above, extract 4), and insists that all the arguments applying to sensible properties (like colour) apply equally to the supposed primary qualities (such as extension and shape): ‘where the other sensible qualities are, there must these be also, to wit in the mind,