1. ‘Progress’ and ‘Tradition’
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Perhaps nothing differentiates the moral ecology of the modern world from that of the pre-modern more than the issue of slavery.  Once taken for granted as an ineradicable, though unfortunate, feature of human life, it has now been ‘abolished’, at least from the range of morally tolerable institutions.  It has gone from being merely ‘a sad fact of life’ (as most of us now might view poverty), to an absolute wrong.  It is common to hear the reminder that, ‘people long ago did not believe slavery was wrong, but now we know that it is.’  This describes a fundamental shift in moral framework, from one based on mere belief to one based on knowledge, and entails that the wrongfulness of slavery was a matter of fact all along, even when nobody (or very few) knew, just as the world was round even when everyone thought it was flat.

For that reason, we often find this observation used as a premise in an argument against moral relativism; that is, the view that morality is essentially a matter of collective convention, and therefore relative to the culture or society in question.  What is right in one culture may be wrong in another, and there is no absolute fact about what is right or wrong for all.  The argument against it is that, if moral relativism is true then slavery would have been right when the vast majority of people believed it was; but we know that slavery is always wrong for everyone, no matter what they or their culture believe about it.  Therefore, moral relativism is false.  Instead, the truth lies with moral objectivism: the belief that there are facts about what is morally right and wrong, that are independent of our collective opinions and so are true for all people and cultures, whatever their beliefs about the matter happen to be.   
  

Ludwig Wittgenstein (1889-1951), considered by many to have been the twentieth century’s greatest philosopher, ends his Tractatus Logico-Philosophicus with the following words: “Whereof one cannot speak, thereof one must be silent." Ray Monk, Wittgenstein scholar and biographer, notes the similarity between this final proposition of the Tractatus – the only book to be published in Wittgenstein’s lifetime, and which, somewhat ambitiously, was intended to settle the problems of philosophy once and for all – and the first line of the Tao Te Ching: “The Tao that can be expressed is not the eternal Tao.” In other words, language is incapable of expressing the highest truths. In order to do that, according to Wittgenstein, one must initially climb up the ladder of thought and language – as provided by his Tractatus – and ultimately throw it away.