
For a sample, suppose a barn burns down right after someone chucks a lighted match in the barn. You can't say that the match was "necessary," the barn could have been struck by lightning or arson and still burned. And the match wasn't "sufficient," because the match probably also needed to fall upon something flammable, like dry hay; there had to be oxygen; etc.
Mackie comes up with a fancy acronym, INUS, but I'll leave unpacking all that aside. One of the more provocative suggestions is that a "cause" is highly contingent on context (that might only be relevant to human observers).
If people harmlessly throw matches into a concrete-floored barn every day, if it's widely accepted as hot match disposal, but one day some joker uses it to store a bunch of oily rags... well, the unusual factor tends to get the blame.
Some from the canon:
Plato: Defence of Socrates, Euthyphro, Crito (translated by David Gallop)The Modes of Scepticism by Julia Annas and Jonathan Barnes (a beautiful collection of texts from Pyrrhonian scepticism and analysis of their arguments; the best way I know to meet ancient scepticism)
Descartes: Meditations on First Philosophy (The Cambridge University Press edition is very good; it's probably worth buying their Selected Philosophical Writings for a good basic Descartes text)
David Hume: An Enquiry concerning Human Understanding and An Enquiry concerning the Principles of Morals (I recommend the Oxford Philosophical Texts editions)
Wittgenstein: Philosophical Investigations (terribly, terribly difficult, but very rewarding)
A few contemporary things:
Gilbert Ryle: The Concept of MindWillard Van Orman Quine: From a Logical Point of View
J. L. Mackie: Ethics: Inventing Right and Wrong
Thomas Nagel: Mortal Questions (short essays, well-written, very accessible)
Bernard Williams: Ethics and the Limits of Philosophy
Michael Smith: The Moral Problem
Specialist, technical, odd:
The Frege Reader by Michael Beaney (for modern logic and the beginnings of contemporary philosophy in the analytic style)J. L. Mackie: The Cement of the Universe: A Study of Causation
William Kingdon Clifford: The Ethics of Belief (he argues, oddly but powerfully, that it's immoral to believe things on insufficient evidence or irrationally - an offense to morality, not just reason)
