“Dyalectica,” says the logical text-book of the middle ages, “est ars artium et scientia scientiarum, ad omnium aliarum scientiarum methodorum principia viam habens,” and although the logic of our day must naturally be utterly different from that of the Plantagenet epoch, yet this general conception that it is the art of devising methods of research, —the method of methods, — is the true and worthy idea of the science. Logic will not undertake to inform you what kind of experiments you ought to make in order best to determine the acceleration of gravity, or the value of the Ohm; but it will tell you how to proceed to form a plan of experimentation.
