There are very real psychological differences that underly the political divide between liberals and conservatives. One of simplest ways think about the differences, although this is a bit of an oversimplification, is that liberals want change, the more radical want revolution, and conservatives want to go back to the way things were. Liberals think the solution to various problems is to change the very foundation of social and political life whereas conservatives think the solution to various problems is going back to the good old days. So liberals want to move toward a secular society, legalize drugs, legalize gay marriage, give equal rights and opportunities to women and minorities, in favor of immigration reform, etc, and conservatives want to go back to an idealized past in which America was a small town farming society, all white, and all Christian. A big part of what underlies this dichotomy is a simple personality trait called “openness to experience,” although there are other factors.
So, the most useful characterization of the political parties in the United States is “Progressive and Conservative.” “Liberal” is sometimes used to describe a person of democratic political allegiance but this adds a bit of philosophical confusion into the mix. A “liberal” is someone in favor of liberty and individual rights, the foundation of all modern democracies is liberal in this sense, and “conservatives” often times value individual liberties as much or more than “liberals,” especially when you factor in the overlap between libertarian tea party types and conservatives.
In philosophy the distinction is framed as “egalitarian vs. libertarian.” Egalitarianism is the view that privileges equality as the central value and libertarianism is the view that privileges liberty as the central value. Conservatism doesn’t really have a central philosophical value, so there is really isn’t a coherent ideology to support it. Conservatives generally rely on the philosophical work of libertarians like Robert Nozick, Milton Friedman, Ayn Rand, etc. to justify their position despite those philosophers being at odds with conservatives on social issues like drug decriminalization and gay marriage.
The problem with the “progressive-conservative” dichotomy is that it is not necessarily guided by clear philosophical, i.e. rational, principles as other factors, desiring social change and desiring social stability, cloud rational judgement on the issues.
I believe that egalitarianism is the right ethical view and I think “liberal” or “progressive” political candidates would be better served by a policy agenda that is more informed by an egalitarian ethical view rather than merely a progressive political party agenda. For example, one area in which this could manifest is in a support for family values and religion. The idea here is that that economic issues are not really the ones that divide us, and if some of the other issues could be de-emphasized we, as a country, could get behind egalitarian social policies.
The truth of the matter is that there is obviously no reason why we shouldn’t be able to as such policies would undeniably benefit the majority. The truth is they would benefit everyone except maybe the top 10% or so.
Now I just need to convince Warren to run as an egalitarian in 2016!