1. 'That in virtue of which' has several meanings: -
2. (1) the form or substance of each thing, e.g. that in virtue of which a man is good is the good itself,
3. (2) the proximate subject in which it is the nature of an attribute to be found, e.g. colour in a surface. 'That in virtue of which', then, in the primary sense is the form, and in a secondary sense the matter of each thing and the proximate substratum of each. - In general 'that in virtue of which' will be found in the same number of senses as 'cause';
4. for we say indifferently (3) 'in virtue of what has he come?' or 'for what end has he come?';
5. and (4) 'in virtue of what has he inferred wrongly, or inferred?' or 'what is the cause of the inference, or of the wrong inference?' -
6. Further (5) 'in virtue of' is used in reference to position, e.g. 'at which he stands' or 'along which he walks'; for all such phrases indicate place and position.
7. Therefore 'in virtue of itself' must likewise have several meanings. The following belong to a thing in virtue of itself: -
8. (1) the essence of each thing, e.g. Callias is in virtue of himself Callias and what it was to be Callias;
9. (2) whatever is present in the 'what', e.g. Callias is in virtue of himself an animal. For 'animal' is present in his definition; Callias is a particular animal.
10. (3) Whatever attribute a thing receives in itself directly or in one of its parts; e.g. a surface is white in virtue of itself, and a man is alive in virtue of himself; for the soul, in which life directly resides, is a part of the man.
11. (4) That which has no cause other than itself; man has more than one cause -- animal, two-footed -- but yet man is man in virtue of himself.
12. (5) Whatever attributes belong to a thing alone, and in so far as they belong to it merely by virtue of itself considered apart by itself.