Introduction

Logic is the part of Philosophy that studies reasoning. More specifically, Logic studies:

• How to define the concept of logical consequence.

• The forms of valid reasoning.

• The methods that distinguish valid from invalid reasoning.

• Logical fallacies: invalid reasoning that seems valid.

Aristotle (4th century BC) was the first philosopher to study reasoning in detail, finding forms of valid reasoning. Since then, Logic has developed as one of the most important formal sciences.

Logic is a key tool to all three scientific methods:

• Deduction uses proofs (demonstrations) as its main method of acquiring new knowledge. Valid proofs are proofs that follow valid rules of reasoning, that is logical reasoning.

• Induction analizes large amounts of data in order to extract general conclusions. Logic provides methods for extracting valid conclusions, the empirical sciences provide the initial data.

• Hypotesis plus deduction employs deduction for extracting conclusions from initial hypothesis, so logic is again employed for the advance of knowledge.