Modern American Conservatism (MAC) is bascially Classical liberalism as understood by the Founding Fathers.
It is a doctrine stressing individual freedom, free markets, and limited government. This includes the importance of human rationality, individual property rights, natural rights, the protection of civil liberties, individual freedom from restraint, equality under the law, constitutional limitation of government, free markets, and a gold standard to place fiscal constraints on government as exemplified in the writings of John Locke, Adam Smith, David Hume, David Ricardo, Voltaire, Montesquieu and others.
It is based on the simple principle that if the function of government is other than to secure and defend the unalienable rights of the people, no freedom is possible.
MACs promote strong national defense and necessary regulation to prevent the citiziens/states from doing violence to each other, but are otherwise suspicious of all but the most minimal government necessary to perform its Constitutional mandates and object to most of a federal welfare state.