ABSTRACT
The opinions people commonly hold including their religious, philosophical or ethical beliefs are often not very well grounded. But in science questions are constantly being raised regarding the bases of specific assumptions. Deduction is the only logically valid rule of inference - it is absolutely reliable. In using it people know that if the premises are true, so also will the conclusion be. But deduction is only applicable when people already know the premises. Discoveries are not made solely on the basis of simple induction. Besides induction science makes use of another inductive method of discovery. It is standardly the case in science that choices have to be made between alternative explanations. A scientist may find that she has proposed several hypotheses on a specific subject or, alternatively, different scientists may be offering conflicting proposals as the explanation of the same phenomena.
