As soon as the mind reaches a universal truth, it sets to work to clarify this truth. Such is accomplished by reference to other facts which the universal is supposed to include; and this application of the general to the particular is _deduction_. _Induction discovers_ the new knowledge while _deduction clarifies_ it.
In this treatment induction as a general process has been subdivided into induction as a mode of inference and induction as a method. _Induction as a mode of inference is the process of reasoning from less general premises to a more general conclusion; whereas induction as a method is a procedure from the observation of individual facts to a realization of a universal truth._ In either case the conclusion of an inductive process always implies more than is contained in the premises. This gives to the conclusion an uncertainty. No induction is absolutely free from doubt except the so-called perfect induction, which form will receive attention in a later section.
All inductive assumptions are made possible because of two laws――_universal causation_ and _uniformity of nature_.
The law of universal causation may be stated in this wise: _Nothing can occur without a cause and every cause has its effect._ “It is a universal truth, that every fact which has a beginning has a cause.”――Mill.
SIMPLE ILLUSTRATIONS OF UNIVERSAL CAUSATION.
The sun rises in the east. The boy throws a stone through the window. A democratic wave sweeps the country. Prices of food stuff are high. The bullet, shot out into space, finally falls to the earth. Each one of these occurrences has a cause.[12]
That universal causation is a fundamental condition of all induction may be further illustrated. The astronomer notes that the stars in the vicinity of Vega seem to be moving outward _from_ a common center; whereas in the opposite part of the sky the stars seem to be moving inward _toward_ a common center. Having observed this phenomenon, the astronomer at once looks for a cause. Finally he decides that the phenomenon is due to the fact that the sun, with his attending family, is moving towards Vega. Arranged, the argument may take this form:
The stars in the vicinity of Vega seem to be moving outward from a common center, whereas in the opposite part of the sky the stars seem to be moving inward, When descending a mountain the trees at the foot seem to move outward from, and those at the top inward toward, a common center, When riding on the train the ties in front seem to move outward while those in the rear seem to move inward. From this we conclude that the sun with the Earth and other planets is moving toward a spot in the sky near Vega. Were it not for the assumption that the phenomenon relative to the stars _had a cause_ there could have been no induction. Moreover, any investigation concerning “democratic waves,” “prices of food stuffs,” etc., must assume as a starting point that these phenomena have causes.