What is logic and why do philosophers study it?
Much of the time philosophers study what other people take for
granted. They ask "Why?" and "How?" when others are content to
accept what seems obvious and in need of no justification.
Philosophy thus involves explanations, arguments, and their
critical evaluation. Here argument is meant not in the sense of
dispute or controversy but in the sense of "arguing (for or
against)", or "making a case (for or against)".
In evaluating arguments and explanations two features are
significant: whether the premises, the "starting points", are
jointly plausible; and whether what is said to follow from them
does so. When we reflect on these features we arrive at logic: the
systematic study of what follows from, and of the relations that
hold within and between, bodies of belief, loosely speaking.
(Loosely speaking, for in logic we are not so much concerned with
what we do accept or believe rationally and what inferences we in
fact make but with rather what one could so accept or believe and
what inferences one would be warranted in making whether or not
one actually does so.)
As an attempt at a systematic theory logic has to start somewhere.
Its "raw data" are our intuitions, our inferential practice, and
our reflective judgments. Now, we have no guarantee that these
cohere well: in fact there are tensions. At the very least, we may
find it difficult to construct a systematic account that
accommodates all, or even most, of the raw data. A systematic
theory may therefore lead us to refine (i.e. revise) our
intuitions and change our practice. Logic is a much less
cut-and-dried affair than many text-books suggest.
Formal logic constitutes a "body of knowledge", not in the sense
that all its findings are incontrovertible facts but somewhat in
the same way as moral philosophy does: in each case there is a
standard set of concepts, theories involving those concepts, forms
of argument and a ragbag of tricky cases that is played off
against intuitions, and perhaps used to subject those intuitions
to critical scrutiny and to refinement. Formal logic is also more
like the sciences than is any other part of philosophy: it aims at
a systematic account of a body of "phenomena" on which there is
fairly widespread agreement and in order to do so it uses formal
methods of representation (a feature of logic that goes back to
the ancient Greeks) and formal techniques. Formal logic is formal
in that it seeks to give a systematic account of the validity of
individual arguments only insofar as they exemplify certain
"patterns of argument". Patterns, or forms, of argument are the
main object of study. It is this feature of logic that allows us
to establish some results in and about logic with the same
exactness as one encounters in mathematics (but at least when
logic is studied as part of philosophy one should not lose sight
of the wider goal).
Two further considerations are often given as reasons for studying
1. Logic is "therapeutic": one learns logic in order to become better
able to recognize and to construct good arguments (in philosophy
or any other discipline).
2. Formal logic is an indispensable item in the contemporary
Learning about any systematic discipline improves one's own abilities
in thinking systematically. And certainly, the methods and techniques
of formal logic are used by some philosophers, mostly those working in
philosophy of language and philosophy of science. Two text-books that
integrate formal logic into a range of topics in philosophy are
Brenner's Logic and Philosophy and Bradley and Swartz's Possible
* The two "Introductions", by Quine and Strawson, reprinted as
Chapters 1 and 2 of R. I. G. Hughes, ed., A Philosophical
Companion to First-Order Logic, Indianapolis: Hackett, 1993.
* Mark Sainsbury, Logical Forms, Oxford: Blackwell, 1991, Chapter 1,
* William Brenner, Logic and Philosophy: An Integrated Introduction,
Notre Dame: University of Notre Dame Press, 1993.
* Raymond Bradley and Norman Swartz, Possible Worlds: An
Introduction to Logic and Its Philosophy, Oxford: Blackwell, 1978.
Text by Peter Milne
HTML Editing by Darren Brierton and Peter Milne