  Like many other logicians of the 19th century, Jevons wants to establish clear links between mathematics and logic. He would like to derive mathematics from logic, which is based on the Laws of Thought, and in doing so he makes (a rather controversial) use of mathematical symbols when establishing his logical formalism.  Jevons denotes terms by capital letters A, B, C, etc. and their negative counterparts by small italic letters a,b,c, etc. The relation of identity or sameness is represented by the sign ‘=’. The expression ‘A ~ B’ indicates that A and B are not identical with each other; ‘A § B’ indicates that there exists any relation between A and B, which includes but is not restricted to the relations of equality or inequality. The general formula of logical inference implies that from A = B § C we can conclude that A § C.  Jevons defines the concept ‘term’ in his Pure Logic: “Term will be used to mean name, or any combination of names and words describing the qualities and circumstances of a thing”. Jevons distinguishes between the extent and the intent of a term or a name. “The objects denoted form the extent of meaning of the term; the qualities implied form the intent of meaning”. It follows that extent and intent of meaning are negatively correlated: when more qualities are added to the meaning of a term, less objects will correspond to that meaning. Abstract qualities, denoted by abstract terms, originate when objects are compared and resemblances and differences identified. Abstract terms possess only one kind of meaning. Substantial terms, such as ‘gold’, denote substances. Nothing is denoted by the symbol ‘0’, which in logic means “the non-existent, the impossible, the self-inconsistent, the inconceivable”. Jevons lists several “special laws” which govern the combination of terms.  The “Law of Simplicity” implies that a term combined with itself has no effect, hence A = AA = AAA = etc. The law of commutativeness indicates that the order of the combination does not matter, hence AB = BA, ABC = ACB = BCA = etc.