Why is the principle of contradiction a necessary, naturally known truth?

The answer to the question involves seeing the order in which rationes arise in our mind.

St. Thomas gives two accounts of the order of the first rationes that arise in our mind. The first is from the Summa Theologiae:

Division falls in the intellect from the very negation of ens. So the first thing that falls in the intellect is ens, second, that this ens is not that one, and thus second we apprehend division; third “one” fourth, multitude

The second is from the Commentary on the Metaphysics:

So the first thing falling in our intellect is ens, and then division, and after this, the one that is the privation of division, and last the multitude that is constituted from the units. For although the things which are diverse might be many nevertheless they do not have the ratio of many things unless after “this and that” there is “one” attributed to it.

Even though every divided thing is a multitude, the ratio of the divided arises prior to the ratio of a multitude. Similarly, each ens that our mind knows is “this” ens or “that” one; but the first ratio of ens is not “this one as opposed to that one”. Rather, the first ratio that the mind forms is ens simply, in such a way that applies to all universally. The mind next considers the limited ens it understands under the ratio of the limited and hence divided from others. In the minds first act, it gets a hold of the absolute and unlimited, which applies to all; in its second act it gets a hold of the exclusion of one being from another. These two acts cause the mind to know absolutely the distinction of being from non-being; that is, the first two acts of the mind constitute the principle of contradiction as an absolute principle. We insist on saying that the principle arises from these first two acts of the mind. The mind does not first form the principle of contradiction and then apply it to “ens” and “limited ens”. Rather the first two rationes in the order of our intelligence are the foundation of the principle of contradiction. So far as the principle of contradiction is taken as the awareness of the opposition between being and not being, taken absolutely, and arising naturally from the first acts of the human mind, the first two rationes of the mind constitute the principle of contradiction.

The principle of contradiction arises from this order of rationes in our knowing: is not a principle arbitrarily set at the beginning of the road to understanding, nor something “programmed into the hardware” of the human mind. Rather, it is the first truth that must be learned by a knower every time he learns about finite objects: for so far as the knower learns, he must go from imperfect knowledge toward perfect knowledge, and so he begins with ens; and so far as he knows finite objects, the first ratio he forms after ens will be of “this ens as opposed to that one”. In the first two steps of our mind, we enter into an absolute perspective, and then see non-ens or privation in opposition to what we know.

In conclusion, the principle of contradiction is natural in the sense that arises necessarily from the knowing operation of an intellect that comes to know finite things by learning. An intellect that did not need to learn, or did not have finite objects as the primary objects of its knowledge would not give rise to the principle of contradiction in the first two rationes of his mind. Here we see another confirmation of the lowness of the human intellect, for this principle is only natural to us because we first know imperfectly (for we come to know by learning) and we first know imperfect things (for every finite thing lacks the perfection of another).

1 Comment

  1. Gagdad Bob said,

    February 8, 2009 at 9:32 am

    I wonder if the vertical distinction between beyond-being and being is an analogue of the horizontal distinction between being and not-being, so that the nihilism of scientistic materialism is a kind of perverse mirror image of the unKnown Godhead….

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