It is weak, ultimately, because its own intellectuals no longer truly believe in it

A very erudite and insightful essay. From Liberalism’s Beleaguered Victory by Abram N. Shulsky.

A very interesting point which I rarely see mentioned when discussions center on the causes of strife around the world.

Liberalism meets with further opposition when the stresses and strains of the transition to modernity are particularly difficult. In the later developing countries, this transition is likely to occur at a faster rate. In the case of England, development of a modern liberal society didn’t occur faster than the rate at which various discoveries enabled industrialization and urbanization. For later adopters, the paradigm of what a developed society looks like already exists, as does the necessary technology, and foreign investment can expedite the transition. Hence, societal change is likely to be more rapid for late adopters than for early ones, creating greater social tension and disorganization, which further erodes liberalism’s popularity and credibility.

And then there is this observation.

Other difficulties stem from more inherent problems or weaknesses of liberalism. Its origins lie in certain philosophic premises, concisely and memorably spelled out in the truths of the Declaration of Independence, concerning the rights with which all men are endowed and the establishment of governments by consent of the governed to protect those rights. As the document says, these truths were then regarded as self-evident; it is reasonable to say they are now hotly contested.

The loss of belief in these principles is reflected, for example, in the works of Comte and his assertion that mankind’s thinking proceeds from a theological stage, via a metaphysical one, to a mature, positive one. In this mature stage, man no longer believes he understands the essence of things, but contents himself with knowledge on the model of modern natural science—knowledge of the “how” but not of the “why” or the “wherefore.” The philosophic bases of liberalism fall within the “metaphysical” period; as the social sciences evolve into a “positive” phase, they concern themselves not with rights or any other kind of self-evident truths that relate to the fundamental character of society (more generally, values), but only with the knowable, objective relationships among variables. The switch to a more “positive” social science holds out the possibility of a more efficient and effective management of society, such as was promised by the Progressive movement of the early 20th century. But it does so at the cost of potentially weakening the hold of core liberal beliefs on society at large.

I think that last point is important. It seems like a lot of discussion are over-focused on how do we solve this preferred problem at all rather than figuring how to do so within the context of core liberal beliefs. In other words, the problem takes precedence over the principles. In the short term, most problems are more easily solved by working outside of constraining principles than within them. In the long term, not so much.

Modern politics, and the modern natural science that developed along with it, depend crucially on de-emphasizing certain human concerns, especially the concern with the afterlife and immortality (a concern at the center of the Christianity that dominated Europe for centuries). Politically, this meant that opinions about salvation had to be regulated either by the political authority (as in Hobbes) or relegated to the private sphere (as in Locke). In either case, the individual’s passionate concern for the fate of his immortal soul had to be tamed or contained; it was no longer to affect actions he might take in the public sphere, at least none that could not be sufficiently motivated and defended on a non-religious basis.

You can look at deemphasizing "the concern with the afterlife and immortality" as a philosophical or psychological or religious issue. Alternately, you can look at as an increase is the time discounting rate. If you are concerned with the far distant future, you have a low discount rate. If you are concerned only with the here and now you have a very high time discount rate. The accumulation of capital is critically dependent on both a high degree of self-control and postponement of gratification as well as a low discount rate on the future. You have to believe that the capital saved through postponed current gratification will be rewarded in the future. Religion tends to both encourage self-control and encourages a low time discount rate. I think Shulsky is right that there is an unintended consequence occurring. By discounting religion in order to foster individualism, there is an inadvertent subversion of progress because the discounting of religion also leads to less self-control and a higher time discount rate.
Shulsky summarizes his argument thus.

So to assess the health of liberal democracy, we must keep in mind two opposing thoughts: It is strong because it opens the way to the satisfaction of the real needs and desires of most people, most of the time; and it is weak, ultimately, because its own intellectuals no longer truly believe in it and because there are seemingly ineradicable longings of the human soul that it ignores or pretends do not exist—and, indeed, that its own liberality encourages into expression.

I think Shulsky is right. Our greatest threat is not from exernal sources or constraints. It is from the abandonment of our core classical liberal principles by our intellectuals. Fortunately, the broad public of our nation are, to a much greater degree than the intellectuals, still wedded to classical liberal ideals. Cycles and cycles. Sometimes intellectuals are the vanguard, sometimes it is the despised bourgeoisie.