36. What means the idea of purely possible being? If we maintain that the object of the idea of being is reality, these two ideas, being, and purely possible, would seem to be contradictory: reality is not purely possible, for were it purely possible, it would not exist, and in the non-existing there is no reality. Let us examine this difficulty, and investigate the origin of the idea of pure possibility. 37. Surrounded as we are by contingent beings, contingent beings ourselves, we are incessantly aware of the destruction of some, and the production of others, that is to say, of the transition from being to not-being, and from not-being to being. Our inward sense attests to us this transition from not-being to being; we have ourselves experienced it; all our recollections are limited to a very brief term, before which the world already existed. Thus, then, reason, experience, and inward sense show us that there are some objects which are, and then disappear, and that others, which before were not, now appear. In those things in which we witness this change, we perceive properties and relations which give occasion to a certain combination of our ideas, and this combination subsists whether the objects to which they refer continue or cease to exist. In this way we form a general idea of things which, although they do not exist, may exist; but this subject _things_, does not express being, but in general finite, determinate objects. 38. Here, then, is the solution of the difficulty. Purely possible being, such as we conceive it to be in the manner explained, involves no contradiction; it does not denote _a reality which is not a reality_, but an object, or a finite, determinate thing, the idea of which we have, although it do not exist, and whose existence involves no contradiction, or repugnance with any of the conditions contained in its idea. The expression, then, purely possible being, if it be explained in this manner, is nothing more than the generalization of these and other similar propositions. A desk which is not is possible. What do we mean by this? Simply that in the idea of desk there is nothing repugnant to its existing; and purely possible being signifies nothing more than that we have many ideas of finite things which may exist without repugnance. The expression refers to determinate things conceived of by us, but we abstract in this case whether this or that be the essence of which we speak, and comprise all those which offer no repugnance.