Ought vs. should
X asks: I am unable to figure out what the special significance is of not having a ‘moral ought’ in the Indian traditions. If ‘should not’ and ‘must not’ have the same practical consequences as ‘ought not’, that is we are obligated to behave in a certain way, why does it make a difference how it is expressed in our language?
Your question is probably the best way of showing the difficulty we have with normative thinking. That is one of conceptualizing something called a normative ethical domain. Let us see if a simple (and simplistic) answer will help. Consider:
(a) You should not play with fire if you do not want to get burnt.
Contrast this with the statement,
(b) You ought not to torture fellow-human beings (if you want to remain a moral human being).
Regarding (a): Is the statement valid if I wear a fire-proof suit, or I use a long non-conductive stick, or move a robot to do that using remote control? Of course not. You can play with fire and still not get burnt. In that case, this statement carries no force whatsoever. In even more simplistic terms, no ‘moral intuitions’ are violated if you play with fire. (You can make the issue as complex as you want, but the point holds.)
Regarding (b): this statement, we think, ‘ought’ to be applicable to all people, at all times and in all circumstances. That is, we believe that this statement is universalizable.
The universalizability is one of the properties of moral statements and it remains valid even if it is empirically false (i.e. even if torture is a practice common across cultures and peoples). The validity of this statement is not affected by anything we do; it tells us what ‘ought not’ to take place even if it does take place regularly. This distinction, between what ‘is’ the case and what ‘ought’ to be the case, distinguishes an empirical statement from a normative, ethical statement.
How do we justify a normative statement? There are many, many attempts and fragments of answers: one says that one justifies by appealing to consequences, others do not believe that this is the proper way provide a justification, and so on. Whatever the case, the point is that moral statements require a justification that typically appeals to some or another ‘norm’ that we accept.
The problem with your question is that ‘should not’ and ‘must not’ do not have the same (logical) consequences as the ‘ought not’. You say they have the same “practical consequences”. Let us assume for a moment that it is so. If that is the case, one could violate the ‘should not’ and ‘must not’ statements without problems [see the (a) above]. Typical of normative statements is that one ‘ought not’ to violate them, even if one does it regularly, in any circumstance whatsoever.
However, if you believe that no such universalizable statements are forthcoming and that ‘should not’ and ‘must not’ can be violated depending upon the circumstances, then what you are claiming is that there is no ethical domain to talk about.
This is merely one aspect of the issue. There are many more. But they all suggest us this: if we think in Indian languages, then we cannot say what the ‘normative’ ethical domain is, why one needs it, what significance it has, and so forth. Herein lies one of the reasons why the West called the Indians “immoral”. (That is, as a people who have no ethics at all.)