Self-acceptance involves accepting personal limitations and possibilities. It is a crucial step in any personal development – you first have to be aware of and accept what's true about your life if you want to be able to then change your life for the better.

There are also limitations and possibilities that we share as members of the human race. If we cannot first be aware of and accept our common human nature, any attempt to change how we are in relation to each other in our personal relationships, or as a country or a culture, is doomed to failure.

We can cause lots of trouble for ourselves and others by failing to accept – or refusing to accept – human nature.

To be specific, most of the greatest evils of the past century in particular have resulted from a kind of perfectionistic idealism. Communism, Fascism, Nazism, and Islamic Fascism are all examples of ideologies that reject the realities of human nature and seek to impose their version of the perfect on humanity as a whole.

There's nothing wrong with idealism in itself – in fact it's been the motive force behind much of mankind's improvement and innovation.

The beauty of America's founding principles is that they are at once idealistic and at the same time firmly grounded in reality. They set a beautifully idealistic vision for humanity: "We hold these truths to be self evident, that all men are created equal, that they are endowed by their creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness…" But then the US Constitution lays out a very practical framework for a government that can actually function to support that vision.

Our founders understood human nature well; and Madison expressed this understanding succinctly in Federalist 51: "If men were angels, no government would be necessary. If angels were to govern men, neither external nor internal controls on government would be necessary." But men are not angels, and those governing us are certainly not angels… and never will be.

For idealism to be useful, for it not to serve evil means toward delusional ends, it must be based on an awareness and acceptance of what's true; particularly, what's true about human nature.

And one great truth of human nature is that, while we might strive for perfection, and we may enjoy blissful moments of perfection, we are not perfect. We make mistakes, we fail, we have weaknesses and we have limitations. While an idea of perfection can inspire us and provide us with a direction, the expectation that we must achieve perfection to be successful is a dangerous notion.

What this expectation can instill in us is a fear of failure; and grappling with failure is absolutely necessary for anybody to achieve the best that they are capable of.

One of the realities of a free society is that it is not some perfect work of final perfection. It is a complex and dynamic system of disparate individuals, joining together and moving apart in what would appear to the idealistic technocrat to be some terrifying dance of chaos.

But the results of course can be truly magnificent.

The idea that people can somehow be made perfect is made possible by a powerful idea, made famous by John Locke, that human beings are a "white paper, void of all characters, without any ideas" upon which experience scratches its words. Locke was arguing against the divine right of kings in the name of human liberty, but as we shall see, this concept – known as tabula rasa, Latin for "blank slate" – has been used for very different purposes since.

The central difference between the left's view of mankind and the classical liberal view is that the left rejects the notion of human nature, and wishes instead to see us largely as blank slates.

Here is the point that I want to drive home: If we were blank slates, it would mean that there is no innate human nature. For the person believing that we are blank slates, the differences between people, in terms of gender roles, wealth, health, and ability, are all the result of learning and experience. They are all dependent upon our education, how our parents treated us, how the government directs us, and what we were exposed to along the way.

To a believer in the blank slate view of humanity, all of these differences – the differences that conservatives and classical liberals take as simply a given of human existence – are unfair and unjust. The idea of social justice is an expression of a passionate sense of injustice at our innate differences.

To a believer in the blank slate, these differences are every bit as unjust and artificial as the differences between monarchs and subjects in earlier societies. The "lottery of life" throws some people into luckier circumstances than others, and that is all that explains the differences in outcome.

This is a powerful force in the worldview of the left. It holds a similar passionate emotional quality as we might experience at the thought of King George abusing his power over the American Colonists; thus some on the left read people like Thomas Paine, and they think that they are resonating with the same spirit of combating injustice. They might read John Locke, and see that he was using the idea of the blank slate as an argument for liberty – and so they can believe that their cause of social justice, taking money from some people to give to others, regulating some to "equalize" them with others, etc., is somehow a fight for liberty.

This, I suspect, is the driving force for at least some on the left, who truly believe that the contemporary use of the word "Liberal" really means one who seeks liberty.

There's just one little problem with this view of humanity; there is no support whatsoever that we are indeed blank slates. We are much more complex than that.

People cannot be simply programmed by society, or teachers, or parents, or community organizers to be whatever they would like us to be. We can be threatened and forced to do certain things against our will out of fear, but we cannot be made different. There is a human nature, and any efforts at improving the human condition has to take our human nature seriously.

But what is this human nature, and what makes it such a powerful and predictable force in human affairs?

We have been called by Aristotle and others a "social animal," but that really doesn't do us justice. There are lots of social animals, from ants to antelope. But we have qualities that are not shared, to any significant degree, by any other organisms on earth. We are more accurately what my favorite social psychologist, Roy Baumeister, calls a "cultural animal."

By culture I don't mean any particular set of habits or rituals from any number of different geographical or ethnic groups. We are cultural beings because we have the capacity to explore and learn and solve problems, and to share our experience, knowledge, and solutions with other people, beyond our immediate connections, and across time.

That we are cultural beings has several consequences: Having a strong sense of self is one of them. We do not just run along with the herd in search of food and circle around our young when danger approaches, we can discover complex and novel ways of bringing food to us; and we can create ways of protecting ourselves from danger, including strategies for settling conflicts before they erupt into threatening scenarios.

There are biological needs, such as food, water and shelter. There are social needs, such as companionship and cooperation. These are part of our human existence. But as cultural beings, we have been required and blessed with needs and capacities beyond biological and social concerns.

The capacity for reason, choice, language, and problem-solving are all a result of our cultural capacity. As Baumeister says, if you are a social animal and you solve a problem, it may be solved for your lifetime; but as a cultural being, once a problem is solved, it may be solved forever.

We have a human nature, which includes both troubling and magnificent elements. These all exist within us, but the overriding quality that makes us human is that we can choose which impulses and feelings and ideas that we want to act upon. We have a conscious capacity to channel our human nature toward better or worse expressions; and we have the capacity as a culture to value some expressions over others.

We are not blank slates to be shaped and molded by force, or social animals who simply go along with the herd, or even lead the herd as "alpha" males do in a pack of wolves.

We are complex cultural beings, with our inborn temperament, heredity and soul. We are influenced and deeply affected by the people and events of our lives. We can be threatened and frightened into acting in certain ways, but we cannot be molded and shaped through force to be "better," according to some administrator's idealistic delusions.

We are human beings; with all the heroic potential, and tragic flaws that have been understood for millennia. By first accepting this truth – as America's Founders did – we can then look clearly at what we can actually do to bring the best of our ideals into practical being.