Logic: An Introduction to Elementary Logic

Logic: An Introduction to Elementary Logic by Hodges, Wilfrid. paperback edition. ISBN: 9780140136364.

Logic is primarily about consistency - but not all types of consistency. For example if a man supports Arsenal one day and supports Spurs the next then he is fickle, but not necessarily illogical. The type of consistency which concerns logicians is not loyalty or justice or sincerity but compatibility of beliefs. Logic, therefore, involves studying the situations in which a sentence is true or valid and subsequently the rules which determine the validity or otherwise of a given argument.