Google Rand Paul today and you'll find stories about him suspending his presidential campaign under "Breaking News." In one way it is; in another it isn't. It's really an old story, but those who don't know history have been doomed (again) to repeat it.

Since William F. Buckley started National Review in the 1950s, libertarianism has been viewed as a subset of conservatism. Reagan affirmed this view in the 1970s, before rising to the presidency selling that same theory.

But what caused Reagan to fail to shrink the federal government (it doubled in size during his presidency) is the same problem that doomed Rand Paul's presidential campaign. Libertarianism and conservatism are antithetical philosophies and any attempt to combine them will fail.

It is important to understand the philosophical differences here, because they do indeed dictate political positions today. I've written an entire book about this, but the crucial difference between libertarians and conservatives is this: true conservatives don't believe man keeps his natural rights when he enters society. Understood properly, they don't even believe they exist in nature at all.

Both Hobbes and Burke said that man in the state of nature "has a right to everything," "even unto one another's bodies," added Hobbes. That puts them into a war of "everyone against everyone." Therefore, they believe the purpose of government is to ensure "the inclinations of men should frequently be thwarted, their will controlled, and their passions brought into subjection," as Burke wrote in Reflections on the Revolution in France.

The chief difference between conservatives like Hobbes and conservatives like Burke are their opinions on the means to thwarting man's natural inclinations. Hobbes believed only absolute power centralized in a unitary sovereign could accomplish the goal. His philosophical heirs in American history included Alexander Hamilton, Abraham Lincoln and George W. Bush.

Burke believed that power must be divided, between branches of government (king and parliament) and central and local governments. His philosophical heirs in American history are John Adams, Barry Goldwater and Ted Cruz.

But whether you're a Hobbesian centralist or a Burkean constitutionalist, as long as you are a conservative you part from libertarians in one very important area: you believe 100% of the power resides somewhere within the government. For constitutionalists, if the federal government isn't going to regulate it, then the state government should. Or the municipal. Or the town. Or your local school board. No power is left to the individual.

Just as true conservatives see man's condition in the state of nature as a war so, too do they see the natural state of nations to one another, unless one nation dominates the rest. This explains why conservatives and libertarians can't agree on foreign policy.

It is also why Thomas Jefferson and John Adams were such bitter political enemies after the revolution, when they had been allies during it. Jefferson, at least in his thinking and writing, if not always in his actions, was what we would today call a libertarian. Hipster libertarians would probably prefer "classical liberal," but there really isn't a difference.

Yes, modern libertarians apply their principles better in theory than 18th century libertarians, just as free market proponents today apply Adam Smith's principles better than he himself did in 1776. But when Jefferson wrote that the purpose of government was to secure inalienable rights, he parted from every conservative in British and American tradition. The Declaration's preamble is a succinct summary of Locke's Second Treatise, where all of its philosophical roots can be found. We know this, because Jefferson said so, more than once.

When Jefferson became president, he declared the purpose of government as to "restrain men from injuring one another, shall leave them otherwise free to regulate their own pursuits of industry and improvement, and shall not take from the mouth of labor the bread it has earned." This is the core libertarian political principle, unchanged in 2016. It's completely at odds with the purpose outlined by Hobbes and Burke.

Jefferson was expressing what libertarians today call "the non-aggression axiom" and it informed Jefferson's policy. Jefferson cut military spending by over 90% in his first term. He truly gutted the military, believing it should be only large enough to provide for defense, never offense. That's how he was able to eliminate all internal taxes and still pay down $57 million of national debt.

This would horrify conservatives today, just as it did then, because conservatives don't believe in libertarian principles. As Russell Kirk told us in The Conservative Mind, even "back in the day," conservative John Randolph "wholly repudiated the common interpretation of the Declaration of Independence, denounced Jefferson as a Pied Piper, and turned his back upon political abstractions to seek security in prescription and in an unbroken vigilance over personal and local rights."

What does this have to do with Rand Paul? Everything. Rand Paul failed even to equal his father's success precisely because he tried to combine libertarianism with conservatism. Where his father applied the libertarian principle of non-aggression, Paul applied constitutional conservative principles.

Where his father said bring all foreign-based troops home, Rand Paul said "don't be too hasty to go to war." That pleased neither libertarians nor conservatives. Both the deployment of troops in nations who have not directly attacked us and forcing taxpayers to pay for anything not necessary for defense violates the non-aggression principle. But it doesn't violate conservative principles. Therein lies the rub.

Where Ron Paul defended legalization of heroine, Paul merely said drug offenses should have lighter sentences. That turned off libertarians and conservatives, for different reasons. Libertarians staunchly oppose laws against drugs based on the non-aggression principle. Conservatives strongly support them, due to their belief that the role of government is to thwart those evil inclinations.

Right down the line, Paul's attempt to fit the libertarian message into a conservative framework killed his chances. His father said sanctions are an act of war; Rand Paul said they weren't. Ron was applying libertarian theory; Rand conservative theory. But conservatives did not want to hear Rand's sensible approach to Iran. So Rand got votes from neither.

Ron Paul's campaign was exciting to both longtime libertarians and new converts precisely because it was so anti-conservative. Sure, Ron Paul said the word "conservative" as a matter of necessity, just as Republicans say the words "free market." But neither really mean it, deep down.

Since the Democratic Party abandoned classical liberalism for progressivism, those classical liberal/libertarian ideas have tenuously resided within the conservative movement, like strangers in a foreign land. It's time libertarians ended their long experiment with converting the Republican Party. America needs a libertarian movement unhampered by the contradictory influences of conservatism.

Tom Mullen is the author of Where Do Conservatives and Liberals Come From? And What Ever Happened to Life, Liberty and the Pursuit of Happiness? Part One.