…that, by virtue of what it is, it necessitates that consequent; otherwise we would not have apprehended the quiddity as such. And once we grasp that, by its very essence, it necessitates a particular consequent, we must then conceive that consequent itself, for knowledge of the relation between two things necessarily includes knowledge of both relata.”
He continues: “Such, then, is what has been said on this question. Yet an objection must be noted. Someone might argue that what is entailed by knowing the quiddity is only the knowledge of its immediate consequent, and that immediate consequent is the proximate cause of a second consequent. In that case one would have to know the second consequent, and from the second the third, so that knowledge of the quiddity would have to yield knowledge of all its consequents, near and remote alike—an impossibility. Hence it is established that knowing the quiddity does not necessitate knowing its consequent.”
He also says: “Moreover, the quiddity of the cause is not predicated in relation to the thing known and its knower, whereas ‘cause’ is predicated in relation to the effect. Therefore the quiddity of the cause differs from its causality, and knowledge of the quiddity of the cause does not entail knowledge of the proof of the effect.
“We reply to this objection as follows: knowledge of the quiddity of the cause entails knowledge of the effect only on another condition—namely, that the concept of the effect be present. Causality is a relational attribute that does not arise from the mere essence of the cause, so knowledge of that essence is not sufficient for knowledge of causality itself. Yet the essences of both cause and effect, by their very natures, necessitate the relational attribute of causality and effectedness. Consequently, once both are conceived, assent to the attribution of one to the other necessarily follows. This is what we mean when we say that a consequent which follows without a middle term is evident in its affirmation.
“And once it is established that conceiving the cause produces assent to the existence of its immediate effect only when the effect itself is also conceived—and since it is perfectly possible for the effect not to be conceived when the cause is—then clearly knowledge of the reality of the cause does not entail knowledge of every…"