inquiry is concerned, lies beyond human Knowledge; for here the nominal and real essences are not coincident:  general propositions of this sort are determined by analogies of experience, in judgments that are more or less probable:  intellectually necessary science of nature presupposes Omniscience; man’s interpretations of nature have to turn upon presumptions of Probability (chh. iii.  Sections 9-17; iv.  SectionS 11-17; vi, xiv-xvi).  In forming their stock of Certainties and Probabilities men employ the faculty of reason, faith in divine revelation, and enthusiasm (chh. xvii-xix); much misled by the last, as well as by other causes of ’wrong assent’ (ch. xx), when they are at work in ’the three great provinces of the intellectual world’ (ch. xxi), concerned respectively with (1) ‘things as knowable’ (physica); (2) ’actions as they depend on us in order to happiness’ (practica); and (3) methods for interpreting the signs of what is, and of what ought to be, that are presented in our ideas and words (logica).

CHAPTER I.

Of knowledge in general.

1.  Our Knowledge conversant about our Ideas only.

Since the mind, in all its thoughts and reasonings, hath no other immediate object but its own ideas, which it alone does or can contemplate, it is evident that our knowledge is only conversant about them.

2.  Knowledge is the Perception of the Agreement or Disagreement of two Ideas.

Knowledge then seems to me to be nothing but the perception of the connexion of and agreement, or disagreement and repugnancy of any of our ideas.  In this alone it consists.

Where this perception is, there is knowledge, and where it is not, there, though we may fancy, guess, or believe, yet we always come short of knowledge.  For when we know that white is not black, what do we else but perceive, that these two ideas do not agree?  When we possess ourselves with the utmost security of the demonstration, that the three angles of a triangle are equal to two right ones, what do we more but perceive, that equality to two right ones does necessarily agree to, and is inseparable from, the three angles of a triangle?

3.  This Agreement or Disagreement may be any of four sorts.

But to understand a little more distinctly wherein this agreement or disagreement consists, I think we may reduce it all to these four sorts: 

I. Identity, or diversity.  II.  Relation.  III.  Co-existence, or necessary connexion.  IV.  Real existence.

4.  First, Of Identity, or Diversity in ideas.