XXXIII

Among Prerogative Instances I will put in the eleventh place Instances of Companionship and of Enmity, which I also call Instances of Fixed Propositions. They are those which exhibit a body or concrete substance in which the nature inquired into constantly attends, as an inseparable companion; or in which on the contrary it constantly retreats, and is excluded from companionship as an enemy and foe. For from such instances are formed certain and universal propositions, either affirmative or negative, in which the subject will be a body in concrete, and the predicate the nature itself that is in question. For particular propositions are in no case fixed. I mean propositions in which the nature in question is found in any concrete body to be fleeting and movable, that is to say accruing or acquired, or on the other hand departing or put away. Wherefore particular propositions have no prerogative above others, save only in the case of migration, of which I have already spoken. Nevertheless even these particular propositions being prepared and collated with universal propositions are of great use, as shall be shown in the proper place. Nor even in the universal propositions do we require exact or absolute affirmation or negation. For it is sufficient for the purpose in hand even if they admit of some rare and singular exception.

The use of instances of companionship is to bring the affirmative of the form within narrow limits. For if by migratory instances the affirmative of the form is narrowed to this, that the form of the thing must needs be something which by the act of migration is communicated or destroyed; so in instances of companionship, the affirmative of the form is narrowed to this, that the form of the thing must needs be something which enters as an element into such a concretion of body, or contrariwise which refuses to enter; so that he who well knows the constitution or configuration of such a body will not be far from bringing to light the form of the nature under inquiry.

For example, let the nature in question be heat. An instance of companionship is flame. For in water, air, stone, metal, and most other substances, heat is variable, and may come and go, but all flame is hot, so that heat is always in attendance on the concretion of flame. But no hostile instance of heat is to be found here. For the senses know nothing of the bowels of the earth, and of all the bodies which we do know there is not a single concretion that is not susceptible to heat.

But to take another instance: let the nature in question be consistency. A hostile instance is air. For metal can be fluid and can also be consistent; and so can glass; water also can be consistent, when it is frozen; but it is impossible that air should ever be consistent, or put off its fluidity.

But with regard to such instances of fixed propositions I have two admonitions to give, which may help the business in hand. The first is that, if a universal affirmative or negative be wanting, that very thing be carefully noted as a thing that is not; as we have done in the case of heat, where a universal negative (as far as the essences that have come under our knowledge are concerned) is not to be found in the nature of things. In like manner, if the nature in question be eternity or incorruptibility, no universal affirmative is to be found here. For eternity or incorruptibility cannot be predicated of any of the bodies lying below the heavens and above the bowels of the earth. The other admonition is that to universal propositions, affirmative or negative, concerning any concrete body, there be subjoined those concretes which seem to approach most nearly to that which is not; as in heat, the gentlest and least burning flames; in incorruptibility, gold which comes nearest to it. For all such indicate the limits of nature between that which is and that which is not, and help to circumscribe forms and prevent them from escaping and straying beyond the conditions of matter.