was almost, but not quite, entirely unlike

[garbage_cnbeta]

The Hitchhiker's Guide to the Galaxy
by Douglas Adams
He was on board an alien spaceship. He helped himself with a cup of drinking produced from an alien drinking machine.

When the Drink button was pressed it made an instant but highly detailed examination of the subject’s taste buds, a spectroscopic analysis of the subject’s metabolism and then sent tiny experimental signals down the neural pathways to the taste centers of the subject’s brain to see what was likely to go down well. However, no one knew quite why it did this because it invariably delivered a cupful of liquid that was almost, but not quite, entirely unlike tea.

I can understand "was almost, but not quited tea" and "entirely unlike tea", but not put them together. They seem to be opposite. What did the author want to express?

 

[owlman5]

It is an unusual way to say that the liquid had a very slight similarity to tea.

I know from my own experience with reading foreign languages that it can be hard to recognize humor in a foreign language. Adams was trying to be funny with that strange comparison.

 

[kentix]

The author is being funny. It's supposed to be a little confusing.

We might normally say something like "X is completely unlike Y".

So he is saying, "the drink is not completely unlike tea, just almost completely unlike tea." There is really no difference. It's not even close to tasting like tea.

 

[dojibear]

it invariably delivered a cupful of liquid that was almost, but not quite, entirely unlike tea.

Grammatically the words between commas are a "parenthetical expression" (a side comment), which is common in English. The same sentence could also be written using parentheses:

it invariably delivered a cupful of liquid that was almost (but not quite) entirely unlike tea.

So "but not quite" is a comment about "almost". The comment is not part of the sentence grammar:

it invariably delivered a cupful of liquid that was almost entirely unlike tea.

Does that grammar make sense? That is how it is intended to read. The comment between comments isn't part of the grammar.

 

[LVRBC]

It is humor, as everyone else has said. However, if you sort out the sentence, you will find the logic. If it was almost, but not quite, entirely unlike tea, then it had a very slight resemblance to tea. It was almost completely different, but not quite, which means not absolutely entirely different.
For example, if you ask me if I've finished my work for today and I say, "Almost, but not quite," I mean that a very small amount of work is still unfinished.

 

[kentix]

But that's a binary choice. You're either done or you're not. What is the opposite of tastes exactly like tea? And what's a little less than that? It doesn't really make sense. There are thousands of things that don't taste like tea.