There are five broad categories into which fallacies fall. The most important division is between the formal fallacies and the infor mal ones, although there are important distinctions between the various types of informal fallacy. Formal fallacies have some error in the structure of the logic. Although they often resemble valid forms of argument, the staircase only takes us from A to B by way of cracked or missing steps. In brief, the fallacy occurs because the chain of reasoning itself is defective. Informal fallacies, on the other hand, often use valid reasoning on terms which are not of sufficient quality to merit such treat ment. They can be linguistic, allowing ambiguities of language to admit error; or they can be fallacies of relevance which omit something needed to sustain the argument, permit irrelevant factors to weigh on the conclusion, or allow unwarranted pre sumptions to alter the conclusion reached. The five categories of fallacy 1 . formal 2. informal (linguistic) 3. informal (relevance - omission) 4. informal (relevance - intrusion) 5. informal (relevance - presumption)
Born in Hull, Pirie is the son of Douglas Pirie and Eva Madsen. As a child, he attended the Humberstone Foundation School in Old Clee, Lincolnshire.
He graduated with an MA (undergraduate) in History from the University of Edinburgh (1970), with a PhD in Philosophy from the University of St Andrews (1974), and with an MPhil in Land Economy from Pembroke College, Cambridge (1997)
Before co-founding the Adam Smith Institute, Pirie worked for the United States House of Representatives. He was a Distinguished Visiting Professor of Logic and Philosophy at the private Hillsdale College, Hillsdale, Michigan, USA. Pirie was one of three Britons living in the United States who founded the Adam Smith Institute.
The Adam Smith Institute is a UK-based think tank that champions the ideas of free market policy. In January 2010 Foreign Policy and the University of Pennsylvania named the Adam Smith Institute among the top 10 think tanks in the world outside of the US. The Institute is "a pioneer of privatisation" in the UK and elsewhere. It has undertaken policy initiatives aimed at replacing state controls and monopolies with opportunities for competition choice in a broad area. The ASI proposed reforms in taxation, public services, transport and local government. It published Douglas Mason's original paper advocating a poll tax or community charge as it was later called.
His work in helping to develop the Citizen's Charter led to his appointment to the British Prime Minister John Major's Advisory Panel from 1991 to 1995.
Apart from his work with the Adam Smith Institute, Pirie is an author in several fields, including philosophy, economics, and science fiction.