ABSTRACT
This chapter shows how and where people's judgements as to matters of truth and fact fall short of what would be required by formal logic, mathematics, and statistics. Logic, maths, and stats, provide us with normative models for judging the truth of certain conclusions: that is, models give us a means of comparing inferences which people do in fact reach in certain circumstances, and their judgements about whether conclusions are valid or not. Logic has sometimes been taken as providing a description of the thought processes by which people make inferences. Inferences in formal logic can be made from so-called hypothetical propositions: 'If a student works hard, then he passes'. Classical logic, from Aristotle's time until quite recently, dealt largely with propositions that are assertions which might be true or false, in four forms, namely all students are intelligent people, no lecturer is lazy, some psychologists are scientists, and some philosophers are not logicians.
