Sec. 10.  The doctrine of the Predicaments, or Categories, is so interwoven with the history of speculation and especially of Logic that, though its vitality is exhausted, it can hardly be passed over unmentioned.  The predicaments of Aristotle are the heads of a classification of terms as possible predicates of a particular thing or individual.  Hamilton (Logic:  Lect. xi.) has given a classification of them; which, if it cannot be found in Aristotle, is an aid to the memory, and may be thrown into a table thus: 

Substance                     [Greek:  ousia]       (1)
{Quantity          [Greek:  poson]       (2)
Attribute  {Quality           [Greek:  poion]        (3)
{Relation          [Greek:  pros ti]       (4)

{ Where    [Greek:  pou]         (5)
{ When     [Greek:  pote]         (6)

{ Action   [Greek:  poiein]        (7)
Modes of Relation  { Passion  [Greek:  paschein]       (8)

{ Posture  [Greek:  keisthai]       (9)
{ Habit    [Greek:  echein]         (10)

Taking a particular thing or individual, as ‘Socrates,’ this is Substance in the proper sense of the word, and can never be a predicate, but is the subject of all predicates.  We may assert of him (1) Substance in the secondary sense (species or genus) that he is a man or an animal; (2) Quantity, of such a height or weight; (3) Quality, fair or dark; (4) Relation, shorter or taller than Xanthippe; (5) Where, at Athens; (6) When, two thousand and odd years ago; (7) Action, that he questions or pleads; (8) Passion, that he is answered or condemned; (9) Posture, that he sits or stands; (10) Habit, that he is clothed or armed.

Thus illustrated (Categoriae:  c. 4), the predicaments seem to be a list of topics, generally useful for the analysis and description of an individual, but wanting in the scientific qualities of rational arrangement, derivation and limitation.  Why are there just these heads, and just so many?  It has been suggested that they were determined by grammatical forms:  for Substance is expressed by a substantive; Quantity, Quality and Relation are adjectival; Where and When, adverbial; and the remaining four are verbal.  It is true that the parts of speech were not systematically discriminated until some years after Aristotle’s time; but, as they existed, they may have unconsciously influenced his selection and arrangement of the predicaments.  Where a principle is so obscure one feels glad of any clue to it (cf. Grote’s Aristotle, c. 3, and Zeller’s Aristotle, c. 6).  But whatever the origin and original meaning of the predicaments, they were for a long time regarded as a classification of things; and it is in this sense that Mill criticises them (Logic:  Bk.  I. c. 3).