Levinas is famous for the claim that ethics is first philosophy - by which he means not only that ethics must not be derived from metaphysics, not even an ‘ontic’ metaphysics ( i.e. an ‘anti-ontological’ ant-metaphysics) like Heidegger’s, but also that all-thinking about what it is to be a human being must begin with such ´ungrounded’ ethics.This doesn’t mean that Levinas wishes to deny the validity of, let us say, the ‘categorical imperative’. What he rejects is any formula of the form ‘Behave in such and such a way because’.
Yet to most people there seems to be an obvious ‘because’. If you ask someone ‘Why should we act so that we could will the maxims of our actions as universal laws?’ or ‘Why should we treat the humanity in others always as an end and never as a mere means?’ or ‘Why should we attempt to relieve the suffering of others?’ , ninety-nine times out of a hundred the answer you will be given is ‘Because the other is fundamentally the same as you’. The thought - or rather the cliché - is that if I realized how much the other was like me I would automatically feel a desire to help. But the limitations of such a ‘grounding’ of ethics only have to be mentioned to become obvious. The danger in grounding ethics in the idea that we are all ‘fundamentally the same’ is that a door is opened for a Holocaust. One only has to believe that some people are not ‘really’ the same to destroy all the force of such a grounding. Nor is there only the danger of a denial of our common humanity (the Nazis claimed that Jews were vermin in superficially human form). Every good novelist rubs our noses in the extent of human dissimilarity, and many novels pose the question ‘If you really knew what other people were like, could you feel sympathy with them at all ?’
But Kantians will point out that Kant saw this too. That is why Kant grounds ethics not in ‘sympathy’ but in our common rationality. But then what becomes of our obligations to those whose rationality we can more or less plausibly deny?
These are ethical reasons for refusing to base ethics on either a metaphysical or a psychological ‘because’. Levinas sees metaphysics as an attempt to view the world as a a totality from ‘outside’, as it were. And like Rosenzweig, whom he cites, Levinas believes that the significance that life has for the human subject is lost in such a perspective. Levinas’s daring move is to insist that the impossibility of a metaphysical grounding for ethics shows that there is something wrong with metaphysics, and not with ethics.