One of the fundamental foundations to modern Western philosophy is Transcendental Idealism. It is a philosophical system founded by the German philosopher Immanuel Kant in the 1700's.
Kant's philosophy argues that "the conscious subject cognizes the objects of experience not as they are in themselves, but only the way they appear to us under the conditions of our sensibility. Thus Kant's doctrine restricts the scope of our cognition to appearances given to our sensibility and denies that we can possess cognition of things as they are in themselves, i.e. things as they are independently of how we experience them through our cognitive faculties."
In layman's terms, Kant argued - against the standard philosophy at the time rooted in that of the great Angelic Doctor, St. Thomas Aquinas - that man cannot know what objects actually are. An example to help illustrate:
According to St. Thomas Aquinas, when a man observes a door, his senses independently pick up the appearances of the door, such as what it looks like, how it sounds, what it feels like, what it may smell like, and even what it may taste like if he were to lick it. These appearances - called "sensible phenomena" in philosophical jargon, or appearances as they are received by the senses - then carry to the intellect (a faculty of the soul) where the intellect connects the data together to form an understanding of the door. The same is true if one looks at any object. We all know, for example, of what a tree is, or what a cat is, etc. In short, our minds conform to the reality of the object we are focused on.
Kant, on the other hand, would claim that despite our senses picking up the phenomena of the door, we can't really say it's a door since we can't see past the sensible phenomena. In other words, the door may not actually be a door. It may actually be, in substance, a jellyfish. An outrageous claim, but you get the point. If Kant were alive today, he might say that if the door were a living, rational being, it might not identify as a door. Now, can you see where this is leading to, yet?
Yet, in a strange twist, even though in principle Kant would deny that the door is actually a door, in practise he would admit it's a door, since he would have to use the door to enter or exit the room. He already knows he can't walk through the walls! So, what we have with Kant is a philosophical mush that says, in effect: The door is only a door when I need it to be a door. Otherwise, I don't know what it is (again, sound familiar?).
Fast-forward to today, and we can see the effects of Kant's mush on society. Three extremely apropos examples of Kant in action:
1. The worshippers of Moloch (i.e. pro-aborts) will claim that the growth inside a woman's womb isn't a human baby, but only a clump of cells. Therefore, it can be sliced and diced and sucked up a tube. However, when the abortionist needs to sell the organs of this clump of cells, he doesn't market them as the organs of a clump of cells, he markets them as the organs of a human baby. Thus, the baby only becomes a baby when the abortionist needs it to be a baby in order to sells its organs. Otherwise, it's just a clump of cells.
2. Leftists today are unable to define what a woman is. We hear them tell us this (ironically, including women!). Yet, if you shut down abortion, all of a sudden these same Leftists will accuse you of attacking women's rights, even though they don't know what a woman is. Or rather, they will only define womanhood when it's convenient to promote abortion or feminism, but otherwise they can't define womanhood. (Question: if a transwoman (man-into-woman) can't define what a woman is, how do they know if they've become a woman?)
3. The Transgender movement claim that gender doesn't exist. Yet, they also claim that you can change your gender and even identify as one of a hundred genders - even though gender doesn't exist. Rather, gender only exists when they need it to exist in order to promote their abhorrent ideology (have you watched What Is A Woman?).
Thus, we see how Kantianism is the bedrock of Leftist Ideology. Its premise is the total rejection of reality - except when reality is needed to promote some perverse cause. This waxing in and out of reality is sure to contribute to the global insanity we observe all around us. And this thought has infected all facets of societal life, most especially politics.
We see, then, that from a human point-of-view, total mush being pushed as serious philosophy has driven modern man completely bonkers, laying the foundation for Leftism and then feeding it afterward. The antidote is for a return to St. Thomas Aquinas and his philosophy that is rooted in Reality - which is none other than Our Lord Jesus Christ Himself. As I often say, the further away from Catholicism a man strays, the more insane he becomes.
St. Thomas Aquinas, pray for us.
Lord Jesus Christ, have mercy on us and set right our minds!