Sentence:  That is why it is so very important that ethical analysis keep clear the problem of decision as to `` permitted '' effects , and not draw back in fright from any conceivable contingency or suffer paralysis of action before possibilities or probabilities unrelated , or not directly morally related , to what we can and may and must <WSD>do</WSD> as long as human history endures . 
Meaning of the word marked with <WSD> tags:  carry out or perform an action