Gottfried Leibnitz (1714)
Source: Monadology (1714). Etext at http://www.uh.edu/~gbrown/philosophers/leibniz/ and Duncan's Philosophical Works of Leibnitz version, both used. Complete.
1. The monad, of which we will speak here, is nothing else than a simple substance, which goes to make up compounds; by simple, we mean without parts.
2. There must be simple substances because there are compound substances; for the compound is nothing else than a collection or aggregatum of simple substances.
3. Now, where there are no constituent parts there is possible neither extension, nor form, nor divisibility. These monads are the true atoms of nature, and, in a word, the elements of things.
4. Their dissolution, therefore, is not to be feared and there is no way conceivable by which a simple substance can perish through natural means.
5. For the same reason there is no way conceivable by which a simple substance might, through natural means, come into existence, since it can not be formed by composition.
6. We may say then, that the existence of monads can begin or end only all at once, that is to say, the monad can begin only through creation and end only through annihilation. Compounds, however, begin or end by parts.
7. There is also no way of explaining how a monad can be altered or changed in its inner being by any other created thing, since there is no possibility of transposition within it, nor can we conceive of any internal movement which can be produced, directed, increased or diminished within it, such as can take place in the case of compounds where a change can occur among the parts. The monads have no windows through which anything may come in or go out. The Attributes cannot detach themselves or go forth from the substances, as could sensible species of the Schoolmen. In the same way neither substance nor attribute can enter from without into a monad.
8. Still monads need to have some qualities, otherwise they would not even be existences. And if simple substances did not differ at all in their qualities, there would be no means of perceiving any change in things. Whatever is in a compound can come into it only through its simple elements and the monads, if they were without qualities (since they do not differ at all in quantity) would be indistinguishable one from another. For instance, if we imagine a plenum or completely filled space, where each part receives only the equivalent of its own previous motion, one state of things would not be distinguishable from another.
9. Each monad, indeed, must be different from every other monad. For there are never in nature two beings which are exactly alike, and in which it is not possible to find a difference either internal or based on an intrinsic property.
10. I assume it as admitted that every created being, and consequently the created monad, is subject to change, and indeed that this change is continuous in each.
11. It follows from what has just been said, that the natural changes of the monad come from an internal principle, because an external cause can have no influence on its inner being.
12. Now besides this principle of change there must also be in the monad a variety which changes. This variety constitutes, so to speak, the specific nature and the variety of the simple substances.
13. This variety must involve a multiplicity in the unity or in that which is simple. For since every natural change takes place by degrees, there must be something which changes and something which remains unchanged, and consequently there must be in the simple substance a plurality of conditions and relations, even though it has no parts.
14. The passing condition which involves and represents a multiplicity in the unity, or in the simple substance, is nothing else than what is called perception. This should be carefully distinguished from apperception or consciousness, as will appear in what follows. In this matter the Cartesians have fallen into a serious error, in that they deny the existence of those perceptions of which we are not conscious. It is this also which has led them 