Halo asked:

Could you evaluate the view that deontology has no practical value?

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Deontology? What's that?

Here's how the Oxford Companion to Philosophydefines deontological ethics:

Moral theories according to which certain acts must or must not be done, regardless to some extent
of the consequences of their performance or non-performance (the Greek dei= one must). According
to teleology or consequentialism, as commonly understood, the rightness or wrongness of any act
depends entirely upon its consequences. Deontology is seen in opposition to consequentialism in
various ways.

In the light of this opposition, one question to ask is which view, the teleological or the deontological,
is the correct view to take of the foundationof moral judgements, what theorybest accounts for the
validity of the moral decisions that we make. But that is not the question you have asked. Your
question is whether deontology has practicalvalue, in other words, whether an ethical theory setting
out 'those acts which must or must not be done' can be of any use to us in making ethical choices,
irrespective of whether or not that theory does in fact provide the correct philosophical account of the
ultimate foundation for those choices.

I wonder if it has occurred to you that the very same question could be raised about
consequentialism, or teleology. Suppose you believe in the consequentialist theory known as
'utilitarianism', according to which the best action is the action that leads to 'the greatest happiness for
the greatest number'. Bernard Williams, a long-time opponent of utilitarianism, points out a very real
dilemma for the consequentialist, that in order to achieve the greatest happiness for the greatest
number, it is necessary that people do notbase their moral decisions on a utilitarian calculation. In
other words, if you are a utilitarian moral philosopher, your view is that, while utilitarianism provides
the foundation that accounts for the validity of our moral judgements, for the majority of persons the
utility principle has little practical value.

By contrast, it seems to me that deontology has considerable practical value. It is true that general
principles like, 'Never tell a lie' do not always help us resolve the moral dilemmas that we face in real
life. When principles clash, as they often do, you have to make a judgement in the light of the actual
circumstances, a judgement that is not guided by any particular principle. However, I believe that
those children who have been taught by their parents, and at school, that there are things which are
right and wrong, that you must, or must not do are still better equipped to make those practical
decisions.

Geoffrey Klempner