26. Those things only are intrinsically impossible which involve the being and the not-being of the same thing; wherefore they are styled contradictory. When an absurdity of this nature is presented to us, we at once recollect the principle of contradiction, and say, this cannot be, "since it would be and would not be at the same time." Why is a circular triangle impossible? Because it would be and it would not be a triangle at one and the same time. The idea of not-being does then enter into that of impossibility: without it, there can be no exclusion of being, and consequently, neither contradiction nor impossibility. 27. Possibility may be understood in two ways: I., inasmuch as it expresses only simple non-repugnance; and then what does not exist, is not only possible when it does not involve any contradiction, but also, the existing, the actual; II., inasmuch as it expresses non-repugnance, united to the idea of not being realized; and then it is only applicable to non-existing things. The possible taken in the former sense, is opposed to the impossible; in the latter, it is opposed to the existing; it involves, however, the condition of non-repugnance. In the former case we have possibility simply so called; in the second, pure possibility. From these remarks we conclude that the idea of possibility adds something to that of being, that is, non-repugnance, non-exclusion; and if there be question of pure possibility, the non-existence of the possible being is likewise added. 28. When the understanding perceives being in itself, it cannot distinguish whether there is or is not repugnance; this is only discoverable by comparison; for the idea of being, in itself simple, does not include comparable terms. The idea of being can encounter no repugnance if it be not applied to some determinate thing, to an essence in which contradictory conditions are imagined, as may be verified by seeking to apply being to a circular triangle. 29. So far is the idea of being in itself from being susceptible of abstraction from the idea of existence, that it is rather the idea itself of existence. When we conceive of being, in all its abstractness, we conceive of nothing else than of existence; these two words denote one and the same idea. 30. We can, in determinate things, conceive of the essence without existence; thus also we can very easily consider all imaginable geometrical figures and examine their properties and relations, abstracted from their existence or non-existence; but the idea of being, as something absolutely indeterminate, if it be abstracted from existence, is also abstracted from itself, is annihilated.