CORRESPONDENCE WITH ARNAULD
Translation © George MacDonald Ross, 1974–1999
Leibniz to Arnauld, 9th October 1687 (GP.II)
[118] . . . . As for this other objection you have raised, Sir, namely that the soul joined to matter does not make out of it a being that is truly one, since matter is not truly one in itself, and that the soul, in your opinion, only gives it an extrinsic denomination, I reply that it is to the animated substance that this matter belongs, and it is truly one being. Matter taken as mass in itself is nothing but a pure phenomenon or well-founded appearance, as are also space and time. [119] It has not even got any precise and definite qualities which could make it pass for a determinate being, as I have already implied in my last letter. For even shape, which is of the essence of a bounded extended mass, is strictly speaking never exact and determinate in nature, because of the actual division to infinity of the parts of matter. There is never a sphere without irregularities, nor a straight line without curves mixed in with it, nor any curve of a certain finite nature without a mixture of some other [nature], and this is true on the small scale as much as on the large. Consequently, far from being constitutive of bodies, shape is not even an entirely real or determinate quality outside thought, and one could never assign a certain precise surface to any body as one could if there were atoms. And I can say the same about size and motion, namely that these qualities or predicates depend on phenomena, like colours and sounds; and although the knowledge they include is more distinct, they are no more capable of standing up to an ultimate analysis. Consequently, extended mass, considered without entelechies and consisting only in these qualities, is not corporeal substance, but a pure phenomenon like a rainbow. Further, philosophers have recognised that it is form which gives determinate being to matter, and those who forget this will never get out of the labyrinth of the composition of the continuum once they have entered it. Only indivisible substances and their different states are absolutely real, as Parmenides, Plato and other ancient philosophers were well aware. For the rest, I agree that one can speak of an aggregate of inanimate bodies as one, even if they are not bound together by any substantial form, as I can say: ‘There is a rainbow,’ or ‘There is a herd;’ but it is a phenomenal unity or a unity of thought, which is not sufficient for what reality there is in phenomena.
[The rest of this extract was enclosed in square brackets, as a sign to the copyist that it should be omitted from the version sent to Arnauld.]
But if one takes as the matter of corporeal substance not mass without forms, but a secondary matter, which is the sum total of those substances whose masses make up the mass of the body as a whole, one can say that these substances are parts of matter in this sense, just as those which enter into our bodies constitute part of it; for as our body is the matter and our soul the form of our substance, so it is with other corporeal substances. [120] And I find no more difficulty here than in the case of man, where there is complete agreement on all I have said. Among other sources of the difficulties which have been raised over these questions is the general lack of a distinct enough notion of whole and part, the latter being basically nothing other than an immediate requisite of the whole, and in some way homogeneous [with it]. Thus, parts can constitute a whole whether or not it has true unity. It is true that a whole which has true unity can remain strictly the same individual even though it loses or gains parts, as we experience in ourselves; thus the parts are immediate requisites only for a period of time. But if one understood by the term ‘matter’ something which would always be essential to the same substance, one could mean (in the sense employed by some scholastics) the primitive passive power of a substance. In this sense, matter would certainly not be extended or divisible, despite being the principle of divisibility, or as much of it as belongs to substance. But I do not want to argue about the use of terms. . . .
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