  On Leibniz's view, to individual substances there belong only perceptions and appetitions, and these perceptions and appetitions can be understood to form a series within the individual substance. In other words, every individual substance can be thought to have a set of perceptions and appetitions such that one could say that, at any given time, a particular substance was experiencing such-and-such a perception and such-and-such an appetition. Indeed, Leibniz's view is that a given substance, x, has, within its individual concept, information of the following sort: x at time t1 will have perception1 and/or appetition1; x at t2 will have perception2 and/or appetition2; and so on. (In fact, the position is more complex; for, as will be shown in a subsequent section, the mind has at any moment an infinity of petites perceptions within it, perceptions of everything that is occurring in the universe, but the human mind at least will be truly aware of one thing at a time. For example, the reader of this article could be said to have a temporally-ordered series of perceptions – with t1 corresponding to the first sentence, t2 the second sentence, etc. – and also “background noise” of which the reader is not directly aware – for example, the sound of an ambulance's siren gradually approaching and retreating from t1 to t3.) Moreover, the series of perceptions and appetitions are generated from within the individual substance itself. That is, Leibniz speaks as if perceptions and appetitions follow naturally from prior perceptions and appetitions – and it is in this respect, after all, that a finite individual substance is causally independent from all other finite created substances.