Posterior Analytics (Bouchier)/Book II/Chapter XIX

Chapter XIX: On the attainment of Primary PrinciplesEdit

Concerning the faculty which acquires knowledge of the ultimate principles of demonstration. These principles cannot be innate, but are derived from repeated sense perceptions which produce memory and experience, the germ of unity or generalisation in the mind. Thus primary principles are derived from induction, and as they are indemonstrable they cannot be learned by Science, but by Pure Reason (νος) which is the Principle of Science.

We have now shewn what syllogism and demonstration are, and how they are effected; and we have also discussed demonstrative knowledge, for that is the same thing as demonstration. We shall understand the primary principles, both as regards the method of their acquisition and the habit of mind which acquires them, if we first settle certain difficulties connected with the subject. It has already (I. c. 2) been stated that it is possible to acquire scientific knowledge by means of demonstration without first explaining the primary and ultimate principles. A question might however be raised as to whether the knowledge of the ultimate principles is or is not the same as demonstrable knowledge, and whether either of them constitutes a science or not, whether there can be a science only of the one class, while some other faculty cognizes the other; likewise whether faculties for attaining primary principles are produced in us without being innate, or whether they are innate and have remained unnoticed.

It would be absurd to say that we already naturally possess these principles, as then we should have a form of knowledge more accurate than demonstration, of which however we remained in ignorance.

On the other hand if we acquire these principles without having had them before, how can we learn and understand anything when no previous knowledge existed? That as we said when dealing with demonstration (I. c. 1) would be impossible. It is clear then that we cannot already possess knowledge of this kind, nor can it be produced in us if we are unable to recognize the principles and have no faculty for acquiring them. We must therefore possess some such undeveloped faculty, but not of such a nature as to be superior to the principles themselves in point of accuracy. This faculty indeed is clearly possessed by all animals, for all have an innate critical faculty which is called Sense-perception. When possessed of this some animals become capable of retaining perceptions, others do not. Those which do not retain perception can have no knowledge outside their separate acts of perception, either none at all or none concerning the object which they are incapable of retaining. The other class, in which perceptions are retained, though also perceiving by means of the senses, still preserve a representation of their perceptions in the mind.[1] As these latter multiply a further distinction may be remarked in them. Some beings attain to a concept as a result of the retention of these perceptions, others never do. From perception then, as we hold, memory results, and from repeated recollections of the same phenomenon comes experience, for memories which are numerically many form but a single experience.

Next, from experience, or from the entire universal which is retained in the soul, the single unit apart from the manifold of sense, which is identical in all particular cases, comes the elementary principle of art and science; if the concern be with production, of art, if with reality, of science. The faculties do not exist distinct in the mind, nor do they result from higher states of consciousness, but from sense-perception. Thus, when one side gives way in battle, if a single man rally, another rallies also and then a third, until the original order has been restored. Now the soul’s nature is such that a similar process is capable of taking place in it also. We will now state again what has been said with some obscurity just now. When one of the atoms of sense has taken its stand in the soul a first universal idea forms therein, for one may perceive particulars by means of an action of the senses, but perception is concerned with the universal, not with the particular man Callias. Then the remaining particulars halt, and the process continues until indivisible and universal ideas are formed. Thus as a result of the perception of such and such animals the general idea of Animal is formed, and this latter serves to form yet wider conceptions.

It is clear that the most primary knowledge is attained by means of Induction, for it is through induction that sense-perception produces the universal in the mind. Now there are different modes of thought by means of which we attain to truth, and some of them are always infallible, while others, as Opinion and Calculation, admit of error. On the other hand Science and Reason are always true, and there is no further class of faculties, save Reason, which surpasses Science in exactness. Since then the principles of demonstration are better known than the demonstrations themselves, and since all scientific knowledge implies conclusion, the principles cannot be the objects of Science. Since further, nothing admits of greater truth than Science except Reason, this latter would seem to be the faculty which has the primary principles as its objects. The above argument will serve to shew that demonstration cannot be its own principle, so that science also cannot be its own principle. If then we have no true form of thought (other than science) except Reason, Reason would seem to be the principle of scientific knowledge. Reason is thus the principle of the principles, and bears the same relation to science as the latter does to all other truths.


  1. Reading ασθανομένοις with the Clarendon Press Edition. A better reading is μ ασθανομένοις: ‘Even at a time when the senses convey no such perceptions.’