Or . . . The Only Real Natural Philosophy.
First of all, all words that describe a state of mind - a creed or belief system or a personal or broad based philosophy - change over time. Even the nature of the language itself changes, so why should it be a surprise that a word that means one thing at one point in time may come to mean another.
Moreover, society changes and evolves. Every century since society first formed - let's be generous and say since 5000 B.C. - the rate at which society changes also increases. This is simply a matter of physics. Ever since 5000 B.C., when the planetary climate became more stable and the pace at which farming produced surplus food (enabling surplus population) increased, population has grown.
At first, it grew slowly but steadily, and then it began to explode in the last two centuries. Obviously, it's exploded the most during the 20th Century, and the pace of population growth has expanded even more in the latter half of the 20th Century and at the dawn of the 21st. Put simply: the more people there are, the faster we make still more people.
So, the rate at which the population has grown has continued to accelerate, and that means that the time it takes for the nature of a word to change decreases with those human numbers. As well, of course, the ability of people to communicate has reached a saturation point which means words are born and die over time spans of only a few years.
Now, with that in mind:
What's a "Liberal?" Interestingly, if you asked someone that question in 1945, just after the War ended, they'd have given you a surprising answer. For example, the Nazi Party's Charter Program of 1920 called for "German's Rebirth in the German Spirit of German Liberty. A modern columnist asked, in the context of that quote, whether they were talking about "positive" liberty ("freedom to") or negative liberty ("freedom from")? It's reductive and therefore incorrect (not that that stops neoconservatives) to simply suggest that the notion of "Liberty" is the "foundational goal" from which Liberals derive their philosophy. For many "Liberals," equality is at least as important, if not more, than "freedom to" or "freedom from." Liberalism expects and understands that the most driving piece of "Liberalism" is resistance to established power. Liberalism assumes - correctly - that power tends to accumulate toward tyranny unless checked. Liberals also want "respect" for people simply because they are people, not because of what those people have accumulated, what titles they have or what other people say those people deserve. If you combine these two ideals, Liberals want a resistance to oligarchical accumulation of power along with respect and equality for people.
Another thing Liberals historically want arises from the expectation that societal "harmony" is effectively impossible. Goals of different people and individual groups are bound to conflict, but Liberals assume that the disharmony would be channeled into competition, argument, exchange, and, therefore, growth. This makes this expected social "disharmony" a strength, not a weakness. Yet conservative reductionists constantly accuse liberals of "pie-in-the-sky" notions of harmony (singing songs around the fire, reading Marx and Engels, sharing everything).
They also accuse liberals of being pessimists. Again, the opposite is true. Liberals are uniquely "optimistic" because they assume, as an outgrowth of the above, that change would be inevitable and on the whole, we continue to evolve the society for the better.
This group of ideals are complimentary. The ideal of liberalism therefore assumes that argument is a "good" thing. This is why Liberals engage in "argument" in a constructive way and why those opposed to liberalism tend to engage in reductive, insulting, or "closed-ear" argument styles (I'm looking at you, Fox News).
This is a concept that you can see played on any "Liberal" channel on radio or TV. True Progressives and Liberals tend to argue with one another in a way that isn't generally insulting or reductive. The smug, smarmy, insulting style of "neoconservative" pundits offers stark contrast.
This isn't accidental. It's not this author pumping up a philosophy with which I tend to far more agree than not. The fact that Liberals engage in "argument" in the classic sense is a direct outgrowth of what Liberals believe and what the Liberalist philosophy presumes.
So why is being Liberal a "negative" thing nowadays? Mostly, and truthfully, it's because conservatives say it is, and that's really all it takes for most people for whom the conservative belief system is a self-indulgent "echo-chamber" exercise. But words have power, we all know this, and over time, even people that don't consider themselves to be in a particular "camp" can be unconscientiously and subtly influenced by the new meaning a word takes on.
The reason that liberalism came to be viewed in the negative is because so many philosophies that truly don't espouse Liberal ideals claimed, nonetheless, to be Liberal systems. For example, Communism was a fanatic excess of "hope" that by uniting behind the proletariat (guided, of course, by the privileged elite), society would be made better. This system called itself a "Liberal" system, and yet it didn't espouse all of the guiding principles of what it meant to be a "Liberal."
What about fascism? Fascism glorified the State and talked about "liberty," but of course it didn't espouse equality and "freedom from" oppression or the tyrannical accumulation of power. Yet Nazi's often called themselves "Liberal" Democrats.
These words stuck. They stuck after the war and they stuck into and through the cold war. It's why Archie Bunker used the word "Liberal" in a pejorative way in the 1970's. The Script writers were recognizing, and tapping into, what was then a negative evolution of the word as a result of residua from earlier in the Century.
At the end of the day, of course, being a "Liberal" is an act of responsibility. It means, if you do it right, that you're willing to listen, and argue with, opinions borne of the same fact patterns but wherein different conclusions are offered. What grinds Liberal's gears more than anything else, however, is that conservatives and other right-wing extremists tend either to ignore facts when they are not convenient (there IS no global warming, if I believe hard enough), or simply make them up (it's just solar flares!), which means that any "argument" in uniquely flawed. When a Liberal calls someone on this, claiming that it's intellectually dishonest to do so, the name calling, reductive smugness, etc., inevitably follows.
Call yourself a "progressive" if you like, or a "new" Liberal, but whatever you call yourself, understand that being a "Liberal" means that you accept change and embrace it, due to its inevitability. It means that you value both "freedom to" (along with the responsibilities that come with) and "freedom from" (ditto). It means that you "argue" responsibly and you keep an open mind because change is inevitable and you've got to be ready for it when it comes. It means that you espouse equality and that any system which allows equality to be tinkered with or which doesn't give everyone the same fair chance is innately a flawed system.
No one said it was easy being a liberal. But take the long view. Since the universe is inevitably changing, it's really the only "natural" philosophy there is.