In “Toward a Cognitive Semantics”, Leonard Talmy writes:
I walked through the tunnel in 10 minutes.
I walked along the shore for 10 minutes.
In both sentences, the time period is the same, 10 minutes, the
traversed path is bounded and finite, (perhaps even the same length),
and the progression of the cited time period is coextensively linked
with the traversal of the path. The main difference between the two
boundedness types is that a sentence with the in type of temporal
phrase indicates that the reference object with respect to which the
path of motion occurs has a physical or conceptual boundary coincident
with the beginning and ending points of the path, while a sentence
with the for type of phrase indicates that there is no such
coincidence and, in fact, that the reference object extends beyond the
path's end points.
“For” means I hadn’t reached the end of the shore after I walked for 10 minutes.
“In” means I had crossed the tunnel after walking for 10 minutes.
However, according to this thread "In a while" vs. "for a while":
haven't for a while
If you haven't seen him for a week, then he was absent for that duration. Because for indicates a limited time, this often implies that the absence has ended (as RegDwighт suggests).
haven't in a while
If you haven't seen him in a week, then he disappeared a week before now.
This usage indicates a time some distance in the past. There is no implication that the period has ended.
Now I am confused. The rules from Leonard Talmy seem to contradict those from the thread. How can I understand the difference between “in” and “for”?
Best Answer
As @user user21497 points out in the "In a while" vs. "for a while" thread you link to, there are large differences in the meaning of in a while and for a while in certain contexts
but only subtle, a subtext (RegDwighт), or negligible (at most) (user 21497), in others:
This should indicate that 'rules' are complex if worth trying to find hereabouts. And John Lawler says effectively that adding negation to an example complicates the analysis enormously.
...............
With your examples,
As Talmy says, the ten minutes is a fixed (if approximate ... say to within a few seconds) timespan, and the implication is that a longer walk was quite possible. As for any implication that the walk has ended: this is governed by the verb (walked) rather than the preposition. 'I have been walking along the shore for 10 minutes' gives no indication that the walk has ended. 'For' does, however, indicate that the time interval being considered has ended (for 'have been walking', from ten minutes ago till now).
sounds most unnatural except as either a claim of a rather fast time for the journey, or an explanation (to someone asking how long a hike would take, or [perhaps under protest] to a police officer querying one's morning activities).
When acceptable, it certainly demands, as Talmy states, that the ten (-nish) minutes was a fixed timespan, and that the whole tunnel was completed. And what other preposition would one use with the paraphrase "I did the tunnel in ten minutes"? One would also say "I walked along the beach in ten minutes" in similar circumstances.
(But note that 'through' actually implies completion also, whereas 'along' usually involves non-completion.)