Rules of law are in fact the institution of conditions under which persons make their arrangements with one another. They are structures which canalize action; they are active forces only as are banks which confine the flow of a stream, and are commands only in the sense in which the banks command the current. If individuals had no stated conditions under which they come to agreement with one another, any agreement would either terminate in a twilight zone of vagueness or would have to cover such an enormous amount of detail as to be unwieldy and unworkable. Each agreement, moreover, might vary so from every other that nothing could be inferred from one arrangement as to the probable consequences of any other. Legal rules state certain conditions which when met make an agreement a contract. The terms of the agreement are thereby canalized within manageable limits, and it is possible to generalize and predict from one to another. Only the exigencies of a theory lead one to hold that there is a command that an agreement be made in such and such a form.[2] What happens is that certain conditions are set such that _if_ a person conform to them, he can count on certain consequences, while if he fails to do so he cannot forecast consequences. He takes a chance and runs the risk of having the whole transaction invalidated to his loss. There is no reason to interpret even the “prohibitions” of criminal law in any other way. Conditions are stated in reference to consequences which may be incurred if they are infringed or transgressed. We can similarly state the undesirable results which will happen if a stream breaks through its banks; if the stream were capable of foreseeing these consequences and directing its behavior by the foresight, we might metaphorically construe the banks as issuing a prohibition.