This list can be reduced to one half the number. Quantity, Quality, Posture, Condition are kinds of _Attribute_ or _Property_ of the Substance. Place and Time are valid. Action and Passion are both referable to causation. Non-causal sequence or consecution (as day following night)--one of the commonest judgments--is not mentioned. The Stoics reduced Aristotle's ten categories to four--Substratum or Substance, the Essential Quality, Manner of being, and Relation. Ka[n.]áda, a Hindu philosopher, has six categories--Substance, Quality, Action, Genus, Individuality, and Concretion or Co-inherence. Plotinus was acquainted with the Aristotelian and Stoic lists and offers as his own:--(1) Fundamental forms of the _Ideal_--Being, Rest, Motion, Identity, Difference; (2) Categories of the _Sensible_--Substance, Relation, Quality, Quantity, Motion. Descartes recognised but two final categories, the Absolute and the Relative. Kant has an elaborate scheme of categories, which he considered to be, not merely classes of judgments, but innate power of the mind by which we are moved to form the judgments. They are the following:-- I. _Of Quantity._ Unity, Plurality, Totality. II. _Of Quality._ Reality, Negation, Limitation. III. _Of Relation._ Of Inherence and Subsistence (_substantia et accidens_). Of Causality and Dependence (cause and effect). Of Community (reciprocity between the active and the passive). IV. _Of Modality._ Possibility, Impossibility, Existence, Non-existence, Necessity, Contingency. Sir William Hamilton's categories were Being, Being by itself, and Being by accident. Categories have also been proposed by Spinoza, Locke, Wolff, Leibnitz, Herbart, Mill, and others. No two of them are alike. They are not formed on any definite principle, but are individual opinions as to the most convenient way to classify judgments[13]. XXII--INHERENCE An object being given by perception we develop our knowledge of it, first by narrowing our focus of attention so as to perceive parts and single attributes of the object; next by widening our attention so as to include several objects in one view. The first process is Analysis or Abstraction; it informs us what attributes co-inhere to constitute the object. The second is Synthesis or Grouping, by which we learn the relations of one thing to others. These operations comprise all we know about a thing, for it can have no attributes which are not either internal or external.