Inference is one of the most important intelligent activities of a human being. We will study different forms of inference and several aspects of its formalization. According to the dictionary:
Inference: every operation leading to the acceptance of a proposition whose truth is not directly known, thanks to its relationship to other propositions known to be true. This relationship can be such that the inferred proposition is judged to be necessary, or only plausible.
Inference is therefore the most general term of which reasoning, deduction, induction, etc. are instances.
Etymologically: to offer → to infer: to carry into – to put forward
Inference is an underlying activity of almost all our other activities. Something as common as vision, for example, uses it (probably without the knowledge of doing so). When we see someone we know, but who has let his beard grow, is wearing glasses (and did not use to before), has put on some weight or lost some weight, etc. we still recognize him, although from the point of view of appearance, this is someone we have never seen.
There are many different forms of inference, among which are inductive (i.e. general conclusion from particular facts), by analogy, from testimonials, from memories, probable inference, statistical inference, non-monotonic, etc.
We begin with the study of one of the most common forms of inference (often carried out unconsciously), which is often mentioned in this book.