Before one is a conservative or a liberal ideologically, or by party affiliation, one is a conservative or a liberal temperamentally, or by disposition. My suspicion is that temperament is a major if not the main determinant of political commitments. First comes the disposition, then come the theoretical articulation, the arguments, and the examination and refutation of the arguments of adversaries. Conservatism and liberalism are bred in the bone before they are born in the brain.
If this is so, it helps explain the bitter and intractable nature of political disagreement, the hatreds that politics excites, the visceral oppositions thinly veiled under a mask of mock civility, the mutual repugnance that goes so deep as to be unlikely to be ascribable to mere differences in thinking. For how does one argue against another's temperament or disposition or sensibility? I can't argue you out of an innate disposition, any more than I can argue you out of being yourself; and if your theoretical framework is little more than a reflection at the level of ideas of an ineradicable temperamental bias, then my arguments cannot be expected to have much influence. A certain skepticism about the role and reach of reason in human affairs may well be the upshot. Pointing to this skepticism I betray my own conservative bias. For surely one of the differences between conservatives and leftists is that conservatives are sober where leftists are sanguine about the power and role of reason in the transforming of society.
I recently found a beautifully pithy formulation of the difference between Left and Right in Jacques Maritain's The Peasant of the Garonne (1968, tr. De Brouwer):
The pure man of the left detests being, always preferring, in principle, in the words of Rousseau, what is not to what is. [footnote by J.M.: "What is not is the only thing that is beautiful," said Jean-Jacques Rousseau. And Jean-Paul Sartre: "The real is never beautiful."] The pure man of the right detests justice and charity, always preferring, in principle, in the words of Goethe (himself an enigma who masked his right with his left), injustice to disorder. Nietzsche is a noble and beautiful example of the man of the right, and Tolstoy, of the man of the left. (pp. 21-22.)
Maritain is of course speaking of ideal types. No sane political philosophy could be purely leftist or purely rightist in the above senses. But it is useful to have the extremes of the spectrum so clearly delineated, especially since political opponents love to paint each other as extremists.