(a) Perhaps it will help us to find out precisely what Value _is_ by seeing as clearly as possible at the outset what it is _not_. It is not _easy_, and never can be made so, to teach and to learn distinctly what Value is in its ultimate nature and constant changes. Here is the one unavoidable difficulty that lies at the very threshold of Political Economy; and this difficulty, which is not found as in the case of "Wealth" in the meaning of the word but in the complex character of that which the word describes, once overmastered, and one walks thereafter with ease and pleasure throughout the economic domain. It would be wrong and cruel to deny that just here is one hard place in the road for teacher and pupils to get over. It arises wholly from the nature of the subject, as we shall soon see, and not at all from the insufficiency of the word, Value. We have already seen fully, that Buying and Selling in each and every transaction is complex and relative, involving twelve elements every time; that Desires and Estimates and Renderings are especially relative,--each party to a trade desires something in possession of the other, estimates that something relatively to something in his own possession, and finally renders to the other his own something for the sake of receiving the other's something. Now everybody is used to all this and practically understands it perfectly, but it is complicated and reciprocal nevertheless, and Value, which is the single birth of the two Renderings, though perfectly intelligible to him that takes pains, is not a thing to be seized once for all at a passing trot. Value, then, is _not_ a quality of single things, belonging to them as if by nature, as hardness is a quality of a rock or gravity is an attribute of gold; because all physical qualities in physical things, all that which makes or helps to make anything such as it is, may be learned by a study of the things themselves by themselves; a careful examination and analysis of the mechanical and chemical properties of any physical thing will discover all its distinguishing characteristics, all that makes it that particular thing in distinction from all other things; but it is plain already, that the _Value_ of anything (if it have value) cannot be found out by studying that particular thing by itself alone; the questioning of the senses however minute, the test of the laboratory however delicate, can never determine how much anything is _worth_, because that always implies a comparison between _two_ things, or more strictly a comparison between two Renderings in exchange. Value is not an attribute of single things: not even if the things be physical and tangible.