The same procedure here required for the conduct of a complete trial, is to be followed also, in miniature, in the production of particulars of evidence. Let us again construe an instance. The _effect_ now is the establishment of the objective correctness of some particular point (made by statements of witnesses, looks, etc.). The _complex of conditions_ consists in the collection of these influences which might render doubtful the correctness--i.e., dishonesty of witnesses, defective examination of locality, unreliability of the object, ignorance of experts, etc. It is necessary to know clearly which of these influences might be potent in the case in hand, and to what degree. The _standardization_ consists, also this time, in the comparison of the conditions of the present case with those of other cases. The _variation_, again, consists in the abstraction from the evidence of those details which might possibly be incorrect, thus correcting it, from various points of view, and finally, in observing the _effect_ as it defines itself under this variety of formulation. This procedure, adopted in the preparation and judgment of each new piece of evidence, excludes error as far as our means conceivably permit. Only one thing more is needful--a narrow and minute research into that order of succession which is of indispensable importance in every natural science. “Of all truths concerning natural phenomena, those which deal with the order of succession are for us the most important. Upon a knowledge of them is grounded every intelligent anticipation of the future” (J. S. Mill).[48] The oversight of this doctrine is the largest cause of our failures. We must, in the determination of evidence, cleave to it. Whenever the question of influence upon the “_effect_” is raised, the problem of order is found invariably the most important. Mistakes and impossibilities are in the main discovered only when the examination of the order of succession has been undertaken. In short: We have confined ourselves long enough to the mere study of our legal canons. We now set out upon an exact consideration of their material. To do this, obviously demands a retreat to the starting-point and a beginning we ought to have made long ago; but natural sciences, on which we model ourselves, have had to do the identical thing and are now at it openly and honestly. Ancient medicine looked first of all for the universal panacea and boiled theriac; contemporary medicine dissects, uses the microscope, and experiments, recognizes no panacea, accepts barely a few specifics. Modern medicine has seen the mistake. But we lawyers boil our theriac even nowadays and regard the most important study, the study of reality, with arrogance. Topic II. PSYCHOLOGIC LESSONS. Section 3. (a) General Considerations.