INFER is a simple computer program that can solve the hypothetical syllogism. A syllogism is a short argument form consisting of one or more premises and a conclusion, which is inferred from the data. Following is a syllogism from the time of Aristotle: Socrates is a man. A man is mortal. Therefore, Socrates is mortal. INFER has four kinds of statements - a) declarations, b) queries, c) requests, d) inquiries. Although queries, requests and inquiries are synonyms, they each have a different function in this program. A: Declarations =============== Data is declared in the following way - -> is A noun phrase consists of an optional article, optional adjectives and a noun, with the predicate 'is' (which must be in lower case). For example, -> Socrates is a man Noted -> A man is mortal Noted B: Queries ========== Queries (which are answered either 'Yes' or 'I don't know') have the following form - -> is a -> is Socrates a man? Yes C: Requests =========== Requests ask for all the data known about something, for example -> request Socrates Socrates is ... man D: Inquiries ============ Inquiries receive more data than a query or a request, for example -> who is a man? Socrates is a man -> who is mortal? A man is mortal The following are rather more complex examples, and show how new relations can be defined in terms of previous ones. -> an impecunious person is a borrower of money Noted -> a composer is an impecunious person Noted -> Mozart is a composer Noted -> is Mozart a borrower of money? Yes -> is Haydn a borrower of money? I have no data concerning Haydn -> Haydn is a composer Noted -> is Haydn a borrower of money? Yes -> who is a borrower of money? composer is a borrower of money impecunious person is a borrower of money Mozart is a borrower of money Haydn is a borrower of money