And there is a second distinctive peculiarity in that comparison that ends in Value, namely, the two things to be exchanged are not compared directly with each other at all, as square and stick are compared, but in the light of the "two desires" with which we are already familiar, and in that of the "two estimates" resulting therefrom. The owner of the wheat desires a trowel, and the owner of the trowel desires a bushel of wheat; the former estimates the effort it has already cost him to procure the wheat in a sort of comparison with the effort that it would otherwise cost him to procure the trowel, and he does not trade unless the trowel seem more and better to him than does the wheat; the latter estimates the effort it has cost him to procure the trowel in a sort of comparison with the effort it would cost him to procure otherwise the wheat that he wants, and he does not trade unless the wheat then and there seem more desirable than the trowel, which he already has; and these two relative estimates of the two owners must _coincide_, that is, the owner of the wheat must think more of the trowel than of the wheat, and the owner of the trowel must think more of the wheat than of the trowel, before these two parties can ever trade. So of all traffic whatsoever. Now the third and last distinctive peculiarity of that kind of comparison out of which Value emerges is this,--an _action_ is necessary in order to complete the comparison. Desires and estimates may have been never so busy, but no Value can ever be born until an outward action takes place in the "two renderings" of our former analysis. Then first we come out upon plain and solid ground. We leave the play of the subjective elements, which yet are essential in the premises, and touch firmly objective realities. _The trowel-maker passes over his tool in the sight of men to the wheat-grower in firm possession and ownership, and takes in return for it from him the grain, which the latter passes over to the former for the sake of receiving the trowel._ The two "satisfactions" follow as a matter of course, and that whole transaction as a commercial exchange and as the sole subject of Political Economy is ended.