Adam Smith, in The Theory of Moral Sentiments, set out what has since become a leading defence for Liberal, secularist morality.

Smith opined it was individual self-interest that held together the moral order of society. As part of individual self-interest, humans–due to their value placed in social relationships–desire the approval of others. To acquire this validation, individuals naturally treat other people in an empathetic, caring manner. Therefore, individual self-interest in acting on our inherent empathy for others, provides the true basis for pro-social behaviour.

As Smith writes of our concern for different people,

How selfish soever man may be supposed, there are evidently some principles in his nature, which interest him in the fortune of others, and render their happiness necessary to him, though he derives nothing from it except the pleasure of seeing it.

Now humans are certainly social creatures by nature, which partly entails a need for approval. As a result, most people avail themselves of the dominant ideas, mores and customs of their time.

That said, the human need for approval–manifesting in prevailing behavioural conformity–is far from necessarily equivalent to moral behaviour. There are two clear reasons for this, which render Smith’s conception of morality woefully inadequate.

First, if immoral practices are routine at a given time and place–as in the Communist regimes of the USSR, Cambodia, North Korea or China–the masses who assimilate themselves to this behaviour out of self-interest will be perpetuating evil.

Second, if individual self-interest is accepted as the only legitimate source of morality, society is ideologically powerless in preventing a preferred self-interest from undermining the moral order.

Consider the hypothetical example of a ten-year married couple–a husband aged 40, a wife aged 35. Throughout this marriage, the husband has earned millions at a private equity firm; the wife has been rearing and raising their 4 children. As in most 10-year marriages, disagreements occur with relative frequency, and their sexual desires for each other have declined. Further, at a time such marital issues have long subsisted, the husband learns his boss has hired a new intern: a voluptuous, vibrant 21-year-old woman. To compound matters, the new intern actively seeks sexual relations with the husband, so to advance her career.

In these circumstances, the husband has a self-interest in acceding to the 21-year-old intern’s pursuit. However, he also has a self-interest in avoiding affair-related guilt and his family’s lasting scorn. Prevailing contemporary wisdom would probably hold that an affair would cause the husband more harm than good, thus being moral in Adam Smith’s sense.

Yet the husband–especially if it were kept confidential–could view his self-interest in re-commencing passionate sexual relations as more important, thereby rationalising an affair. Notably, this is the case for many moderns–Ashley Madison has 60 million worldwide users that are married or in relationships, whose Liberal slogan enticed: “Define your experience, and live life to the fullest! Life is short. Have an affair.”

Evidently, by using individual self-interest as an all-encompassing framework for decency, Adam Smith’s moral thesis can be used to facilitate adultery. And who knows what other immoral permutations, expressly justified in the name of individual self-interest.

In all likelihood Smith–along with fellow Liberals of the 17th, 18th and 19th century–did not foresee how individual self-interest and autonomy could lead to such severely anti-social outcomes as adultery.

But on examination, this can be put down to a lack of imagination; rather than principle. Certain norms, values and institutions were historically assumed; even as Liberals undermined their philosophical foundations through promoting individual autonomy. So when Liberalism was spread amongst racially homogenous, Christian populations, of course certain decisions were off the table; of course individual autonomy would be balanced by other considerations; of course proper conclusions would be reached

But as individual autonomy increasingly compromised our pre-existing moral assumptions, over time, people felt excused to behave in unforeseen, socially destructive ways. And we have the popularity of Ashley Madison to show for it.

Adam Smith’s morality thus becomes untenable, and to paraphrase the words of Patrick Deneen in Why Liberalism Failed, it cannot perpetually enforce order upon autonomous individuals who are increasingly shorn of constitutive social norms.