Deduction and induction – theory

New knowledge is not created out of thin air. But it is the outcome of the process that we call inferring. It is the combination of existing knowledge to create new knowledge. We derive than truth or assumed probable truth through the truth of other statements, This we do by use so-called premises and conclusions. We put premises together in a coherent way in order to lead us to a conclusion.

A premise is a thing that we might call true. We list these in a way so that they make sense. Following them comes a conclusion. Which is the end point of our reasoning, at least of this particular argument. Premises are therefore parts of arguments. They are say propositions that we use to defer a conclusion. Basically an argument consists of at least two premises and one conclusion.

This structure of two premises and one conclusion forms the basic argumentative structure. More complex arguments can use a sequence of rules to connect several premises to one conclusion, or to derive a number of conclusions from the original premises which then act as premises for additional conclusions.

There are several ways to do so, but the two most important structures are deduction and induction.

Deduction: from the general (theory) to the specific (practice). For example:

  • All men are mortal
  • Socrates is a man
  • Socrates is mortal
  • All ducks here have the same colour
  • I saw a brown one
  • All ducks are brown

Induction: from the specific to the general. For example:

  • Socrates is in jail
  • People in jail usually broke the law
  • Socrates broke the law