With respect to the part of Vital Principle by which it both knows and reflects, whether that part be separate, or separate, not substantively but, in an abstract sense only, let us now consider in what it is distinguished from other parts, and how thinking is at any time exercised. If thinking be such as is feeling, then it may be some kind of impression by the subject of thought, or other analogous agency. But then that which thinks must be impassive, receptive of the form of objects, and, in potentiality, the same as the object, without actually being so. The mind, in fine, must be related to subjects of thought as the sensibility is to objects of perception. It is, then, necessary since the mind thinks upon all subjects, that it should be homogeneous, in order, as Anaxagoras expresses himself, that it should domine, that is, recognise things; and as whatever is foreign to it precludes and eclipses its inward light, so it can have no other nature than that of potentiality. Thus, the so-called mind of Vital Principle (and by mind I mean that part by which Vital Principle judges and compares), is not actually any one of the subjects of thought before thinking upon it. It is very improbable, therefore, that the mind should have been commingled with the body; for were this the case, it would be a quality of some kind, as hot or cold, or it would have some kind of organ as there is for the sensibility, but no such organ is to be found. It is well said by some that Vital Principle is the place of forms, only this is to be understood of Vital Principle, not as a whole but as a cogitative faculty, and of forms, not in reality but, in potentiality.
It is manifest, from the nature of the sentient organs and sensation, that the quiescent state of the sentient is not the same as that of the cogitative part. For the sensibility is unable to distinguish impressions in excess, as a sound amid loud sounds, or a colour or odour among brilliant colours or pungent odours, but the mind, on the contrary, when thinking intensely upon any subject, can still think and with increased rather than diminished intensity upon the subordinate details; the sensibility, besides, cannot be without a body, but the mind is separable. When thus situated, the mind can become each of the subjects of thought, as an individual is said to be learned actually (and this may be said when he is able at will to employ his learning,) because he is at the same time equally learned in potentiality, although not as he was before he had learned or invented something; for when so learned he is able to reflect upon his learning.
There is a distinction between positive magnitude and ideal magnitude, water and ideal water, and so between many but yet not all substances, as with some the two states are identical, but the mind judges of flesh and ideal flesh either by some different faculty or by being itself differently disposed; for flesh cannot be without matter, but, as is a snub nose, it is something in something. Now, it is by the sensibility that we judge of hot and cold and other properties of which flesh is the standard; but it is either by some distinct faculty or as a curved is to an extended line, that we judge of ideal flesh. Straightness, on the other hand, as well as the snub nose we place among abstractions, for each is associated with continuity; but the difference, if there be a difference, between positive straightness and ideal straightness, the mind judges of by some other, perhaps a dual faculty; by some other faculty, at least, or by being itself differently disposed. To use a general expression, as are things abstracted from matter so are subjects of thought with respect to the mind.
It is difficult to determine how the mind, if it be as Anaxagoras supposes, homogeneous, impassive and without any thing in common with aught else, is to think, if thinking be some kind of impression; for it is only in so far as there is something in common between two substances, that the one seems to act and the other to be acted upon. And there is the same difficulty if the mind itself is intelligible; for it will be present in other things, unless it is itself, intelligible in some other way than they are, and unless the subject of thought is some one specific subject; or else the mind will be some kind of combination, and this reduces thought to the nature of other things. But to suffer impression according to some common relation implies, as has been just explained, that the mind, in potentiality, is as the subjects thought upon, and yet that, in reality, it is no one of them before thinking upon it; and thus the mind is to be regarded as a tablet on which nothing may have been actually inscribed. The mind is a subject of thought to itself as is any other topic, since that which thinks and the subject of thought are among immaterialities; for speculative knowledge is the same as the subject which is so known. But we have to consider why the mind is not always thinking, as each subject of thought, in potentiality, is among materialities; so that the mind will not be present in any one of them (for the mind is the immaterial faculty which judges of them), although each of them will be subject to the mind.