Every fundamental investigation must first of all establish the nature of its subject matter. This is the maxim of a book, “Über die Dummheit”[46] (1886), one of the wisest ever written. The same axiomatic proposition must dominate every legal task, but especially every task of criminal law. It is possible to read thousands upon thousands of testimonies and to make again this identical, fatiguing, contrary observation: The two, witness and judge, have not defined the nature of this subject; they have not determined what they wanted of each other. The one spoke of one matter, the other of another; but just what the thing really was that was to have been established, the one did not know and the other did not tell him. But the blame for this defective formulation does not rest with the witness--formulation was the other man’s business. When the real issue is defined the essentially modern and scientific investigation begins. Ebbinghaus,[47] I believe, has for our purpose defined it best. It consists in trying to keep constant the complex of conditions demonstrated to be necessary for the realization of a given effect. It consists in varying these conditions, in isolating one from the other in a numerically determinable order, and finally, in establishing the accompanying changes with regard to the effect, in a quantified or countable order. I can not here say anything further to show that this is the sole correct method of establishing the necessary principles of our science. The aim is only to test the practicality of this method in the routine of a criminal case, and to see if it is not, indeed, the only one by which to attain complete and indubitable results. If it is, it must _be of use_ not only during the whole trial--not only in the testing of collected evidence, but also in the testing of every individual portion thereof, analyzed into its component elements. Let us first consider the whole trial. The _effect_ is here the evidence of A’s guilt. The complex conditions for its establishment are the collective instruments in getting evidence; the individual conditions are to be established by means of the individual sources of evidence--testimony of witnesses, examination of the premises, obduction, protocol, etc.