Union with Christ bestows inner exaltation, consolation in suffering, calm assurance, and a heart that is open to love of mankind, to all that is noble, to all that is great, not out of ambition, not through the desire for fame, but only because of Christ. (quoted in the Baker Encyclopedia of Christian Apologetics, p. 443).
Who was this devout teenager? Dwight Moody? Charles Spurgeon? No, though it may be hard to believe, it was Karl Marx, who would one day become arguably the world's most influential atheist. Marx's family was Jewish in origin, but his father had officially converted to Lutheranism when Marx was six years old. However, while a university student, Marx turned to atheism and became a strong opponent of religion, famously calling it "the opium of the masses."
And yet, despite his rejection of God, Marx was actually unable to completely escape the influence of theistic beliefs. Indeed, Marx is an excellent example of those atheists, who, in the words of Christian apologist Frank Turek, "steal from God." That is, Marx, like many other atheists, based his view of the world on certain ideas that necessarily derive from belief in God.
Perhaps the most obvious case of Marx's (unconscious) reliance on theism was his beliefs about morality. Marx quite clearly rejected the idea that there are moral absolutes--that there are some things that are always right or always wrong. In fact, as is noted in The Baker Encyclopedia of Christian Apologetics:
[In Marxism there] are no moral absolutes. There are two reasons for this. First, there is no external, eternal realm. The only absolute is the unfolding dialectic world process...
Second, there is no foundational nature or essence for general principles of human conduct. Ideas of good and evil are determined by the socio-economic structure. Class struggle generates its own ethic. (p. 442)
In other words, since Marxism is materialistic, it rejects the existence of a realm outside the material universe from which would come eternally-existent moral standards (often viewed as having been established by a divine Lawgiver). Moreover, whatever moral standards there are that do exist among human beings are determined by the dominant socio-economic class and are, hence, entirely arbitrary and change with the evolution of society.
Nevertheless, even though Marx rejected the notion of moral absolutes, he often wrote as if absolute standards of right and wrong existed. Consider, for example, this denunciation of the bourgeoisie, the putative ruling class in capitalist society:
The bourgeoisie, wherever it has got the upper hand, has put an end to all feudal, patriarchal, idyllic relations. It has pitilessly torn asunder the motley feudal ties that bound man to his 'natural superiors,' and has left remaining no other nexus between man and man than naked self-interest, callous 'cash payment.' It has drowned the most heavenly ecstasies of religious fervor, of chivalrous enthusiasm, of philistine sentimentalism, in the icy water of egotistical calculation. It has resolved personal worth into exchange value, and in place of the numberless indefeasible chartered freedoms, has set up that single, unconscionable freedom—Free Trade. In one word, for exploitation, veiled by religious and political illusions, it has substituted naked, shameless, direct, brutal exploitation.
Note Marx's use of words and phrases like "pitilessly," "naked self-interest," "egotistical calculation," and "naked, shameless, direct and brutal exploitation." Marx is not engaging here in a dispassionate analysis of society; he is expressing moral outrage at the actions of the bourgeoisie. However, such outrage would seem to be predicated on the existence of moral standards by which the actions of the bourgeoisie may be judged as wrong. But if there are no moral absolutes, as Marx claims to believe, then he has no right to employ such moralistic language. Moreover, if notions of right and wrong are determined by the dominant socio-economic class, then presumably in a capitalist society the reigning morality would be that of the bourgeoisie, and by these standards, their actions would not be in any way problematic. Furthermore, if Marx wanted to argue that bourgeoisie morality is somehow deficient, he would have to do so on the basis of moral standards that transcend those of capitalist society, that is to say, moral absolutes. Indeed, from a logical viewpoint, if "ideas of good and evil are determined by the socio-economic structure," how could Marx have even been able to transcend the morality imposed by the "socio-economic structure" of his own times?
In short, it is obvious that Marx's views on morality were fundamentally contradictory. In effect, he attacked the bourgeoisie for violating moral standards whose existence he denied. In reality, he was unable to escape the need for moral absolutes. And yet, such moral absolutes ultimately must originate with a divine Lawgiver since it can be shown that they cannot have their basis in nature or human society. In other words, like other atheists, Marx had to assume the existence of something--a transcendent morality--which would not exist if God did not exist. Perhaps if Marx had held to the beliefs he professed in his youth, he would not have been forced into such intellectual confusion, and, given the great evils committed in the name of the political philosophy he fathered, the world might have been a far better place as well.