Hi, thanks for your reply, loyts of food for thought. I m not assuming that all humans believe that preservation of the specie is a good thing ( there are flat earthers and people convinced that the theory of evolution is a satanic lie, imagine if there can be a general consensus on ethical issues ). I m just saying that the account of humans= rational and political (social) animal amf of morality= human phenomenon aimed at human flourishing are pretty sound and convincing, one can always come up with a better account but so far and in the last ...2300 years the alternatives were and are way less convincing. If we agree on the account of humanity and of morality I have sketched supra than some actions are objectively wrong, even if they are widespread. Of course this is really roughly put and presupposes a number of metaphysical commitments ( personally I m convinced that....everything in philosophy presupposes a certain metaphysic, implicitly or explicitly) but metaphysics ethics etc can and should be the result of rational inquiry not of a more or less arbitrary choice ( i.e. is not my choice that humans have cognitive abilities that make them different from other animals or that they are social beings etc). Does it make any sense?