Bones likes alcohol a lot and assumes Spock will get to like the taste if he persists, and then they can all go to the pub and drink and Spock will still be able to drive them home?

Bones likes alcohol, but has inhibitions about drinking alone?

Bones likes alcohol, but likes messing with Spock's head even more?

I love "Devil in the Dark." There's also a funny anecdote about it in Nimoy's autobiography: For some reason, Shatner was off set when they filmed the mind meld scene (the back you see is apparently the stunt double) - family illness, or something like that, and after he came back, Shatner cornered Nimoy in th canteen, and asked him to describe how he'd played it, to help him prepare for filming the reaction shots. Nimoy obliged.

Shatner said, no, he couldn't picture it, could Nimoy act it out? So Nimoy did, obviously very sotto voce, as they were in public. Shatner persisted, saying he still couldn't picture it, Nimoy would have to do it properly.

Eventually Nimoy cracked, and did the scene, culminating with him crouching on the floor, giving an agonised cry of "THE PAIN!!!!!"

At which every head in the canteen turned and Shatner, the picture of innocence, yelled "Jesus, could someone get this poor guy an aspirin!"