Those ideas are also adequate which follow in the mind from ideas which are adequate in it. For when we say that an idea follows in the human mind from ideas which are adequate in it, we do but say that in the divine intellect itself an idea exists of which God is the cause, not in so far as He is infinite, nor in so far as He is affected by the ideas of a multitude of individual things, but in so far only as He constitutes the essence of the human mind.
I have thus explained the origin of those notions which are called common, and which are the foundations of our reasoning; but of some axioms or notions other causes exist which it would be advantageous to explain by our method, for we should thus be able to distinguish those notions which are more useful than others, and those which are scarcely of any use; those which are common; those which are clear and distinct only to those persons who do not suffer from prejudice; and, finally, those which are ill-founded. Moreover, it would be manifest whence these notions which are called second, and consequently the axioms founded upon them, have taken their origin, and other things, too, would be explained which I have thought about at different times. Since, however, I have set apart this subject for another treatise, and because I do not wish to create disgust with excessive prolixity, I have determined to pass by these matters here.
But not to omit anything which is necessary for us to know, I will briefly give the causes from which terms called Transcendental, such as Being, Thing, Something, have taken their origin. These terms have arisen because the human body, inasmuch as it is limited, can form distinctly in itself a certain number only of images at once. If this number be exceeded, the images will become confused; and if the number of images which the body is able to form distinctly be greatly exceeded, they will all run one into another. Since this is so, it is clear that in proportion to the number of images which can be formed at the same time in the body will be the number of bodies which the human mind can imagine at the same time. If the images in the body, therefore, are all confused, the mind will confusedly imagine all the bodies without distinguishing the one from the other, and will include them all, as it were, under one attribute, that of being or thing.
The same confusion may also be caused by lack of uniform force in the images and from other analogous causes, which there is no need to discuss here, the consideration of one cause being sufficient for the purpose we have in view. For it all comes to this, that these terms signify ideas in the highest degree confused. It is in this way that those notions have arisen which are called Universal, such as, Man, Horse, Dog, etc.; that is to say, so many images of men, for instance, are formed in the human body at once, that they exceed the power of the imagination, not entirely, but to such a degree that the mind has no power to imagine the determinate number of men and the small differences of each, such as color and size, etc. It will therefore distinctly imagine that only in which all of them agree in so far as the body is affected by them, for by that the body was chiefly affected, that is to say, by each individual, and this it will express by the name man, covering thereby an infinite number of individuals; to imagine a determinate number of individuals being out of its power.
But we must observe that these notions are not formed by all persons in the same way, but that they vary in each case according to the thing by which the body is more frequently affected, and which the mind more easily imagines or recollects. For example, those who have more frequently looked with admiration upon the stature of men, by the name man will understand an animal of erect stature, while those who have been in the habit of fixing their thoughts on something else, will form another common image of men, describing man, for instance, as an animal capable of laughter, a biped without feathers, a rational animal, and so on; each person forming universal images of things according to the temperament of his own body. It is not therefore to be wondered at that so many controversies have arisen amongst those philosophers who have endeavored to explain natural objects by the images of things alone.
The Three Kinds of Knowledge
From what has been already said, it clearly appears that we perceive many things and form universal ideas:
1. From individual things, represented by the senses to us in a mutilated and confused manner, and without order to the intellect. These perceptions I have therefore been in the habit of calling knowledge from vague experience.
2. From signs; as, for example, when we hear or read certain words, we recollect things and form certain ideas of them similar to them, through which ideas we imagine things. These two ways of looking at things I shall hereafter call knowledge of the first kind, opinion or imagination.
3. From our possessing common notions and adequate ideas of the properties of things. This I shall call reason and knowledge of the second kind.