tide

.
'On' here suggests a boat which is on the water.

For your information, here is the original:
The mere habit of joining any crowd that is going into any lift swept me in on the tide.
Doesn't seem like it's about a boat, or is it?

.
There is no boat-- and for that matter, there is no tide. It is all metaphorical. You asked why 'on', and it is 'on' because tides carry boats on them.

I have no difficuty understanding 'tide' as a metaphor for the flow of people. But boats...I wonder what kind of boats they are in the author's imagination...

.
The whole phrase is the metaphor, Taka.

Boats ride in on the tide of the ocean :: The speaker (like a boat) was swept in on the crowd (like the tide)

TakaWhy not 'It swept me in the tide'?

sweep in is a phrasal verb. In the case at hand, "to sweep something into the interior of something else", namely, the lift. So "It swept me in the tide" would be "It swept me into the lift the tide"! There's no preposition before tide to show how it relates to the rest of the sentence. And if you take

I would agree with MM and CJ here; thus "on the tide" describes the manner of "sweeping in", and "in" makes "sweeping" directional.

MrP

The mere habit of joining any crowd that is going into any lift swept me in on the tide.

This makes little sense to me. How can the habit of joining a crowd sweep you in on a tide, metaphorical or otherwise? Surely it's the crowd itself that does that? The tenses seem screwed up too.

Yes; the "tide" is simultaneously the "habit" and the "people", in this metaphor. Only quantum linguistics can resolve the wave-particle duality.

MrP

I don't think the statement is saying that the crowd caused the sweeping in. I think the speaker could have decided not to enter the lift. According to this statement it seems to me that the speaker's willingness to go along with any crowd, to do as others are doing -- a willingness established through habit -- is what impelled the speaker into the lift. Surely desire, if not literally habit, c