The ability to understand another's emotions is called empathy. The ability to understand another's reasoning is called ______ (what)?

Question

This question is motivated by discussions like the following that I've seen/had from time to time:

Jane: "X believed it would eventually become a danger and that doing this-or-that would stop the danger, which explains why X did this-or-that."

Bill: "But it wouldn't become a danger. And doing this-or-that wouldn't have worked."

Jane: "I didn't say it would become a danger or that this-or-that would work. I said X believed these things to be true, which is why X did this-or-that."

Bill: "It doesn't matter what X believes. It would never be a danger and he shouldn't have done this-or-that."

Bill appears to be unable to understand X's reasoning.

If it had been X's emotions that Bill wasn't able to understand then we'd say that Bill lacked empathy. But since it's instead X's reasoning that Bill can't understand, we say that Bill lacks _____ (what)?

Answer 1

Why not… understanding.

Barmar proposed this answer in a comment and I find it compelling.

un·der·stand
/ˌəndərˈstand/
verb

1. perceive the intended meaning of (words, a language, or a speaker).
   perceive the significance, explanation, or cause of (something).

2. interpret or view (something) in a particular way.
   infer something from information received (often used as a polite formula in conversation).
   regard (a missing word, phrase, or idea) as present; supply mentally.
   assume to be the case; take for granted.

3. be sympathetically or knowledgeably aware of the character or nature of.

Answer 2

The ability to understand another's reasoning is called "reason". The "faculty of reason" or "the power of reason" or "the ability to reason" or simply "reason" (synonymous phrases) is what allows us to identity assumptions and follow the flow of logic.

To answer your question about "Bill": Bill has made some false assumptions.

Answer 3

I would say he lacked sagacity:

the quality of having or showing understanding and the ability to make good judgments:

His air of kindness and sagacity tempts people to confide in him. (Cambridge)

the quality or an instance of being sagacious; penetrating intelligence and sound judgment (Collins)

However, in psychology there is the term cognitive empathy:

Cognitive empathy, also known as empathic accuracy, involves “having more complete and accurate knowledge about the contents of another person’s mind, including how the person feels,” Hodges and Myers say. (Lesley University)

Answer 4

"Enlogossy" ... what else?

But there are other perspectives which may be worthwhile (see what I did there?).

The Wikip page on empathy is quite interesting: it talks of "cognitive empathy" as "the ability to understand another's perspective or mental state". And suggests a handful of other synonyms: "empathic accuracy, social cognition, perspective-taking, theory of mind, and mentalizing are often used synonymously...".

But clearly all these represent a wholly unacceptable betrayal/distortion/perversion of etymology. And, frankly, it is impossible to understand a mind which would reject "enlogossy" in favour of these gallimaufries, coined in an evil hour, which are nothing but the fruit of "corrupted bastard-bearing wombs".

Answer 5

Perhaps the closest a single word gets is rapport, but it is used for examples rather than the global concept of understanding:

rapport [noun] [singular count, or noncount]:

a good understanding of someone and an ability to communicate well with them:

• We'd worked together for years and developed a close/good rapport.
• She has an excellent rapport with her staff.

[Cambridge Dictionary]

However, I'd say that this is a hypernym, as empathy, openness and a collaborative attitude are also denoted.

...............

Actually, I might well use a phrase:

• If two people are on the same wavelength, they find it easy to understand each other and they tend to agree, because they share similar interests or opinions.

[Collins]

But it's a phrase, and hypernymic (knowing another's thinking processes doesn't entail agreeing with them).

As @Barmar suggests,

• Jill [really] understands John

in context has the desired meaning.

Knowing where John is coming from is another metaphor.