Adam Smith did not have to invoke utility maximisation to conceive of the invisible hand, nor did Ricardo to discover comparative advantage: two of the most counterintuitive, and most enduring, cornerstones of economics.
Ronald Coase famously stated that “there is no reason to suppose that most human beings are engaged in maximising anything unless it be unhappiness, and even this with incomplete success”; yet this (half tongue-in-cheek) assertion did not prevent him from formulating a theorem about the superiority of private contracts even with externalities, provided property rights are carefully laid down.1  ¹  Actually, as is well known, Coase did not formulate a “Coase theorem”, but he did lay down the theoretical foundations to what is known by that name.