The theory of incorrect reasoning in the linguistic philosophy of the seventeenth century

The paper aims to investigate the mechanisms of incorrect and misleading reasoning described first by the Port-Royal authors and then by Locke in his Essay on human understanding. The analysis was conducted with particular reference to argumentative fallacies - which are widespread today in information and communication policies – and to the abuse of words, i.e., when the speaker uses a word by changing its meaning to suit his purposes. These strategies are used to influence people’s behaviour and forge public opinion in ways advantageous to political power systems; identifying and explaining these strategies is one of the crucial tasks of critical thought today.