The leftist is fundamentally a humanist.  Those on the left believe that humanity can solve its own problems, that history is the story of slow but inevitable improvement, and that God is an antiquated, retrograde illusion.  Conservatives believe that humanity makes at least as many mistakes as advances, and that we do better when we preserve long hallowed standards – typically those bequeathed to us by God.

From the humanist's perspective, his is the only worldview that can possibly make any sense.  This is true whether the humanist in question is an educated philosophical naturalist, a rabid Marxist, or just a garden-variety nonbeliever who doesn't give our place in the universe more than a passing thought.  Ultimately, however, humanism actually has more to do with its own version of faith than with reason, and the confidence of humanists has more to do with human psychology than with the soundness of their arguments.

At the very deepest level, almost all humanists presume, generally without even thinking about it, that the three-pound brain human beings possess just happens to have the capacity to grasp anything in the universe that is there to be grasped.  Protagoras said, in the 5th century B.C., that "man is the measure of all things." Most people still believe that, whether they are conscious of it or not.  No one would hesitate to acknowledge that the brain of a rat has limitations.  This is self-evident when you look at the rather limited achievements of ratkind.  However, when it comes to our own brains (which modern science insists are functionally synonymous with our minds), we tend to assume that the universe stops conveniently at our capacity to understand it.  This is what "a rejection of supernaturalism" means.  It is the belief that things beyond our grasp do not exist.  This belief actually has no rational warrant.  The rat cannot see any meaning in a book – yet books are not mere piles of paper.  When the humanist sneers at a belief in the unseen, it is because he trusts the capacity of his own mind to explain a world revealed through the narrow lens of human senses.

Of course, today's humanists certainly do believe in unseen things like radio waves – which can be detected with machines.  Much of science is devoted to making the invisible visible, the inaudible audible, and so forth.  However, we are still constrained – not only by our three-pound brain, but by the analogical limitations of our human senses.  We can make impressive telescopes and sound-amplifiers, but we can't really understand anything we cannot at least imagine by analogy to something we ourselves can see or hear.  The nucleus of an atom isn't really a collection of tiny spheres looking something like a bunch of grapes.  That is just a picture of reality imaginable to us.  We are creatures of analogy and metaphor.  Language is metaphor.  Mathematics is metaphor.  We can discover nothing on our own that is so removed from our own human experience as to be completely alien.  How could we?  The humanist believes that there is nothing out there to be found.  The Christian believes otherwise because experience beyond the capacities of his senses has been put inside him.

Humanism is a mirror that reflects admiringly on humanity.  This isn't hard to figure out – it's in the name.  When people take apart the physical world, those material things that we can grasp, they make astonishing progress.  They learn chemistry.  They invent technology.  They revel in man's own achievement and abilities.  However, when people turn their analytical minds on the problem of their own condition, they invent provisional theories at best and unsupported narratives at worst.  The "science" of psychology consists of one rejected theoretical program after another.  Freud is debunked.  The neo-Freudians are debunked – though both Freud and his disciples live on in legend as heroic precursors of the postmodern counterculture.  Behaviorism, though it left behind all sorts of useful methodologies, is debunked in its central thesis – that what happens inside the brain (or the mind) is basically irrelevant, because other people's behavior is all we can actually see.

In general, the hard sciences have added new knowledge from generation to generation, while the social sciences have suffered periodic revolutions – always managing to invent theories that just happen to fit the prevalent biases among intellectuals of their times.  This tendency for the social sciences to enjoy a certain detachment from empirical evidence has evolved in its own sweet all too human way.  Freud's theories never claimed any evidence beyond the authority of Freud's own anecdotal experiences.  That was enough to satisfy the intellectuals of his time.  Diederik Stapel's social narratives, needing a thicker veneer of scientific respectability to suit the contemporary fashion, stood on evidence he simply fabricated as needed.  In the social sciences, the phrase "scientific study" is not the golden seal of truth, but just the golden seal of academic groupthink.

The humanist is a confused creature.  He somehow believes he is free to create a human utopia by the power of his own efforts, but at the same time, he believes in a clockwork universe that runs on the dead logic of physical matter alone.  These two beliefs are contradictory on their face.  In a clockwork universe driven by raw physical and evolutionary forces, human beings pursue not utopia, but rank self-interest.  Nor is it reasonable to assume that utopia is some sort of Darwinian byproduct, evolving blindly by the fixed processes of nature.  It hasn't done so up until now.  Individual survival is one thing – universal happiness is quite another.

Where can this hope for the ultimate perfection of man come from?  Not from reason.  Not from evidence.  Yes, we have amazing technologies all around us – but humanity itself is little changed in its capacity for the ugliest varieties of predations.  I remember an incident a few years ago in which a mother in a nearby city made an inventive use of modern technology – by killing her baby in a microwave.  She certainly had no doubts about her own "dignity" or "worth."  Nor is there any reason to believe she was motivated by any antiquated religious superstitions.

At its formation during the Enlightenment, humanism was very much the product of Christian values.  Like it or not, equality, concern for others, and the sanctity of human life are Christian ideals.  Unfortunately, without the underpinning of God's eternal standards, humanism redefines itself periodically, just as psychology does.  Its real character is now more Marxist than enlightened.  We have gone from a state of tyranny to the ideal of freedom to the dream of equality to the farce of social justice.  This is a complete circle, since social justice is just tyranny with a superficial branding overhaul.  Humanism, like the postmodern notion of truth, is whatever the current authorities say it is.

Science, the unofficial guarantor of humanism, was born in a belief in an absolute and unbending truth.  The sanctity of truth is also a Christian value.  Science cannot flourish in a relativist society.  Already I have heard the peculiar phrases "white science" and "white facts" – as though different races might, perhaps, negotiate different relationships with gravity or move through time at different rates.  If this nonsense is calmly tolerated long, we can shove the scientific advances of centuries in the microwave, too.

The humanist wishes to rid himself of God so that he can, himself, become God.  We've seen this movie before.  It doesn't end well.