Metaphysics is almost always an attempt to prove the incredible by an appeal to the unintelligible.
Interpretation
This quote suggests that metaphysical arguments often rely on abstract concepts that are difficult to understand.
H. L. Mencken highlights the idea that metaphysics frequently seeks to validate extraordinary claims through reasoning that is not easily comprehensible. This can imply that such arguments may lack solid grounding and can lead to skepticism about their validity, as they depend heavily on concepts that seem beyond human understanding.
In practice
In a discussion on the nature of reality, you might use this quote to emphasize the challenges of metaphysical arguments.
I know a good many men of great learning-that is, men born with an extraordinary eagerness and capacity to acquire knowledge. One and all, they tell me that they can't recall learning anything of any value in school. All that schoolmasters managed to accomplish with them was to test and determine the amount of knowledge that they had already acquired independently-and not infrequently the determination was made clumsily and inaccurately.
It takes a long while for a naturally trustful person to reconcile himself to the idea that after all God will not help him
It is the theory of all modern civilized governments that they protect and foster the liberty of the citizen; it is the practice of all of them to limit its exercise, and sometimes very narrowly.
The central belief of every moron is that he is the victim of a mysterious conspiracy against his common rights and true deserts.
The cure for the evils of democracy is more democracy.
It is my conviction that no normal man ever fell in love, within the ordinary meaning of the term, after the age of thirty.
Silence is ever speaking; it is the perennial flow of language.
The very beginning of Genesis tells us that God created man in order to give him dominion over fish and fowl and all creatures. Of course, Genesis was written by a man, not a horse. There is no certainty that God actually did grant man dominion over other creatures. What seems more likely, in fact, is that man invented God to sanctify the dominion that he usurped for himself over the cow and the horse.
Eretz Israel will be restored to the people of Israel. All of it. And forever.
Punishment is the last and the least effective instrument in the hands of the legislator for the prevention of crime.
It is hard enough to remember my opinions, without also remembering my reasons for them!
Reincarnation contains a most comforting explanation of reality by means of which Indian thought surmounts difficulties which baffle the thinkers of Europe.
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