Besides these two kinds of knowledge, there is a third, as I shall hereafter show, which we shall call intuitive science. This kind of knowing advances from an adequate idea of the formal essence of certain attributes of God to the adequate knowledge of the essence of things. All this I will explain by one example. Let there be three numbers given through which it is required to discover a fourth which shall be to the third as the second is to the first. A merchant does not hesitate to multiply the second and third together and divide the product by the first, either because he has not yet forgotten the things which he heard without any demonstration from his school-master, or because he has seen the truth of the rule with the more simple numbers, or because from the 19th Prop. in the 7th book of Euclid he understands the common property of all proportionals. But with the simplest numbers there is no need of all this. If the numbers 1, 2, 3, for instance, be given, every one can see that the fourth proportional is 6 much more clearly than by any demonstration, because from the ratio in which we see by one intuition that the first stands to the second we conclude the fourth. To knowledge of the first kind we have said that all those ideas belong which are inadequate and confused, and, therefore, this knowledge alone is the cause of falsity. Moreover, to knowledge of the second and third kind we have said that those ideas belong which are adequate, and therefore this knowledge is necessarily true. It is the knowledge of the second and third, and not that of the first kind, which teaches us to distinguish the true from the false. For he who knows how to distinguish between the true and the false must have an adequate idea of the true and the false, that is to say, he must know the true and the false by the second or third kind of knowledge. _Reason and Imagination_ It is in the nature of reason to perceive things truly, that is to say, as they are in themselves, that is to say, not as contingent but as necessary. Hence it follows that it is through the imagination alone that we look upon things as contingent both with reference to the past and the future. How this happens I will explain in a few words. We have shown above that unless causes occur preventing the present existence of things, the mind always imagines them present before it, even if they do not exist. Again, we have shown that if the human body has once been simultaneously affected by two external bodies, whenever the mind afterwards imagines one it will immediately remember the other; that is to say, it will look upon both as present before it, unless causes occur which prevent the present existence of the things. No one doubts, too, that we imagine time because we imagine some bodies to move with a velocity less, or greater than, or equal to that of others.