when I put two and two together

[Coffee Break]

Hello everyone. I encountered this expression, "when I put two and two together", but am struggling to understand it. Could you please let me know what it means in the following sentences:

In my pocket I also felt the folded oversized invitation card on which the address of the party was printed in spirited filigree. I vaguely recalled, while talking to Clara at the party, that I’d frequently encounter this card in my pocket and would absentmindedly twiddle its corners, experiencing a sudden burst of joy when I put two and two together, and, in the fog of distracted thoughts, remembered that if the card was still damp from the storm, this could only mean I’d just come in from the snow, that the party was still young, that we were hours away from parting, and that there’d be plenty of time for anything to happen. And yet, even if behind these bursts of joy lingered something like light resentment for being dragged to this party, only to be stood up by my father’s friend, still, it may not have been resentment at all but yet another cunning way of allowing my thoughts to stray from where they wished to linger, only to be pulled right back to Clara and to the uncanny suspicion that Pooh might even have orchestrated a bit of what had happened tonight. Father died. I promised to look out for him. Lonely. Doesn’t know what to do with himself. Meet people.

- André Aciman, Eight White Nights, First Night

This is a novel published in the United States of America in 2010. This novel is narrated by the nameless male protagonist. The protagonist meets Clara at a Christmas party in Manhattan. Here, the protagonist came out of the party and is on the street. In his pocket, he finds an invitation card for the party. (He was invited by his late father's friend named Pooh and promised to meet him at the party, but Pooh had stood him up.)

Here, I wonder what the underlined expression means.
Would that mean that the protagonist made the two corners of the invitation card to meet the other two corners of it...? But this is just my guess.

I would very much appreciate your help.

 

[Tarheel]

When you put two and two together you come to the conclusion you should come to if you think logically. At least, that's the way I see it.

 

[Coffee Break]

@Tarheel,

Thank you very much for the explanation.
I was guessing that perhaps there was a hidden meaning, but I think I thought too much. Then it would really mean adding two to two...
In that case, this is just my small question, but would "two" here mean "two corners of the invitation card", meaning that the four corners of the card came together, rather than the number two, meaning adding two to two becomes four...?

 

[SoothingDave]

It's not literally about two of anything. It's about doing a simple bit of thinking and coming to a conclusion.

Imagine being a parent and your kid has a stomach ache. You're all worried about what might be the cause.

Then you see a bunch of candy bar wrappers in his trash can. You put two and two together and you know why he has a stomach ache.

 

[Coffee Break]

@SoothingDave,

Thank you very much for the explanation!
So "put two and two together" is an idiomatic expression to mean "think logically"!

So he experienced a joy when he thought logically (=put two and two together). He reasoned, and figured out something through thinking. Though exactly what he thought reasonably here is not clearly stated, I guess.

I sincerely appreciate your help.

 

[Tarheel]

@Coffee Break He simply figured something out. (It's unclear what that was.)