One of the peculiarities of the modern condition is its corruption of language. Concepts that were once readily intellectually accessible are now cloudy and muddled to the vast majority of people because the language we use to discuss them has been warped. Although the general effect has been to draw a veil of uncertainty over knowledge of pretty much everything premodern, the exact nature of this muddling varies depending on the word.
In some cases, words have acquired contrary meanings. "Faith" was once understood to be something more akin to "trust": trust in what one's reason has revealed to be true, no matter how much one's senses may scream out against it. You have faith, for instance, that a rope and hook tested on 10,000 pounds weights will hold your comparatively meager frame when you go mountain climbing: you know it's irrational to believe there's much more than a vanishingly small chance you'll die, but still you must force yourself to let go and swing. But today, faith is understood to mean something quite different: a kind of blind, irrational, groping hope against hope, utterly unmoored from any basis in reality. I'm assuming this probably comes from the triumph of fideism in the larger body of religious thought, although it's certainly wound up a convenient means of denigrating a perfectly rational dogma.
In other cases, words or phrases that once would have been understood to be nonsensical have acquired meaning, carrying along them with particular ideas. For instance, the phrases "good person" and "bad person" are ontologically meaningless: the former a tautology, the latter a non sequitur. Yet they're widely bandied about today, especially in service to liberal causes, e.g., "homosexuality can't be immoral, I know plenty of gays that are GOOD PEOPLE." At best, the phrases are heuristics: "good people" really means "people who do good things." But that hardly means those same people don't also do bad things, or even principally do bad things. The problem with even talking that way is that, since everyone does some mix of good and evil, the judgment that one is a "good person" is necessarily subjective and informed entirely by what you've witnessed of them. Thus we're always surprised when some seemingly nice, quite fellow snaps and kills people, and the common refrain is heard (but never listened to) that he seemed like such a good guy. Our understanding of good and evil itself is made hazy with such talk.
There are also curious cases in which two perfectly innocuous words acquire some other (usually sinister) meaning when juxtaposed. I'm reminded of some vaguely right-wing columnist (I think a National Review type) remarking that "social" was a word which, in modern parlance, had the remarkable ability to completely destroy the meaning of any word joined with it, so that "social justice" is typically grossly unjust, "social engineering" lacks the methodological rigor of traditional engineering fields, and "social studies" usually involves the unstudious distortion of history to fit the official modern narrative of slavery/genocide/bigotry/oppression/intolerance rememberance.
Even "modernity" itself is a bizarre word. When I first started to develop an inkling that there was something fundamentally wrong with the world (back in my last year of college), I started looking up what I could about the concept. Unfortunately, much of it had been written by art historians, who seized on the concept of modernity and developed from it the grotesque visual abortion that is modern art. Much of the rest was unintelligible gobbledygook written by pondscum sociologists. Nowhere was I able to find a clear and succinct explanation of what modernity actually was, what it meant, when it started, who was responsible for it, and so on; that realization came gradually as I read more history and philosophy. I almost wonder if that obfuscation isn't intentional, at least in the sense that the whole modern project has been intentional, as if the moderns are deliberately hiding the fact that there is an antiquity against which modernity can be contrasted.
Some words have had additional and previously unheard of meanings attached to them, so that, for instance, "duty" is honored as a virtue rather than simply acknowledged as a fact of human life arising from nature.
Other words have been severed from their traditional connotations, so that "illegitimacy" is seldom thought of as a problem (and the fact that previous generations saw far lower rates of illegitimacy than we have today as a source of concern is simply baffling to most people). No one talks or cares about "divorce" as a problem anymore. On the topic of sex and marriage, that which is "natural" has ceased to mean "that which accords with human nature" (a definition that logically excludes, for instance, homosexuality) and come to mean "that which occurs in nature" (a definition that excludes nothing). Relatedly, "disorder" has come to mean merely "dysfunction," to the exclusion of its more traditional connotation relating to the use of a healthy and functional faculty in a manner that does nto accord with human nature.
The fact that words themselves have fallen victim to modernity's ever-spreading poison just goes to show how deeply the modernist/leftist project has triumphed. I don't even have to make the obligatory 1984 reference. The rot has, at last, reached the heart of the world, and salvation for many people is impossible simply because the language needed to communicate the core concept of it is rapidly disappearing.