One of the objections to Donald Trump is that he's not a conservative. The problem with that objection is that it rarely gets beyond the label. What is conservatism? And why should I care? How is that relevant to my needs?
This is not a simple question to answer, because it's a big question. There are varieties of conservatism. Moreover, conservatism is, in some measure, mutually defining in relation to liberalism, and vice versa. For purposes of this post, I will state my own position.
Liberalism and conservativism evolve over time, in reaction to socioeconomic circumstances. I'm not interested in the history of the concept. Likewise, liberalism and conservatism are subject to national differences, based on the history of a given country, as well as the modern-day issues and circumstances. To some degree, I'm going to discuss this from the standpoint of an American in 2016, during a presidential election year. That will make it a bit provincial and ethnocentric. However, there are transcultural elements to a conservative political philosophy as well.
Another factor is the distinction between secular conservatism and Christian conservatism. My definition will reflect the latter emphasis.
Of necessity, my post will speak in generalities. Obviously, there are many exceptions and variations.
In general, liberals think there's more that's wrong with the world than conservatives. Liberals are chronically discontent with the status quo. Something always needs to be changed. If you succeed in "fixing" one problem, you move on to the next problem. It's an endless task.
To some degree, liberals and conservatives also disagree on what the problems are. Disagree on what's wrong. So, by definition, they differ regarding the solution. If you don't think there's a problem in the first place, you won't agree on the answer.
Liberals view social problems as the result of inequitable access to material goods, as well as improper cultural conditioning. The cause of evil is due to external factors.
They view human nature as a blank slate. To the extent that social problems are caused by cultural conditioning, they can be corrected by cultural conditioning. Education is a key remedy.
Now, theoretically, some liberals think human nature is not a blank slate. We're the product of evolution, our animal ancestry, our genes, hormones, brain chemistry, &c. But when it comes to law and policy, liberals act as though human nature is a blank slate.
As a result, liberals think government is fundamental and central to resolving social problems. Only the force of government can produce uniform results. The job of government is twofold: (i) create equal access to material goods; (ii) retool human nature to create a harmonious society of like-minded individuals. Citizens are members of the hive, conditioned to believe and behave alike, to ensure cooperation between the many individuals who compose society.
Liberalism places a tremendous emphasis on social control, with an enlightened ruling class on top.
By contrast, conservatives are more content with the world. They find fulfillment and happiness in family, friends, religion, work, sports, hunting, hiking.
They think humans have an evil streak. That's ineluctable. Gov't is necessary to keep crime at manageable levels. The job of gov't is not to prevent crime or eliminate crime, but cut it down to size. Keep crime from getting out of hand. Given our evil streak, there's an inbuilt limit on our ability to solve social problems. Moreover, the effort can be counterproductive: stamping out evil puts some evildoers in charge of other evildoers.
So there's a precarious, unstable balance. The ruling class is no wiser or better than the underclass. Indeed, it may be worse. Power corrupts.
Conservatives consider law enforcement to be a supplement to self-defense rather than a substitute for self-defense.
Although some conservatives are reflexively deferential to the authorities, other conservatives realize that human evil poses a dilemma for statecraft: who polices the police?
Many conservatives take a fairly live-and-let-live approach how other people behave. In general, what you do with your own life is none of my business. I may disapprove, but I'm not responsible for how you live for your life. All things being equal, there's the right to be let alone.
For conservatives, you only cede power to gov't when necessary, for things that only gov't can and should do. The best government is the least government.
Conservatism has a culture war aspect to it, viz. abortion, euthanasia, the queer/transgender mafia, parental rights, religious liberty, school choice.
Conservatives support national security, although they disagree on the details of foreign policy.
Unlike liberals, conservatives don't think inequality is inherently wrong. Certain kinds of inequality are wrong. Arbitrary inequalities. Imposed inequalities. But some inequalities reflect natural differences or different priorities between one person and another, or between men and women.
Conversely, liberalism has protected classes with super rights. So there's a tension between equality and inequality in liberal ideology.
Conservatism stresses the distinction between innocence and guilt whereas liberalism tends to attribute criminality to material deprivation.
In general, conservative policy is more about deterring certain actions while liberal policy is more about compelling certain actions. Conservatism sets a moral floor for socially acceptable conduct while liberalism is more ambitious and idealistic.