Why can't a fish survive out of water?

Why can't a fish survive out of water? There are two different responses to this question:

(1) Because a fish's gills do not work in the air.
(2) Because a fish does not have lungs.

Both of these answer the question, although the former is perhaps the response that comes more naturally to mind.

Determining why something happens is like determining the cause of an event: You imagine a world in which the event does not occur; the imaginary world must also lack the cause. For example, consider the collapse of the Tacoma Narrows Bridge on 7 November 1940. The bridge collapsed because of strong winds on the 7th of November; for without those winds, the bridge would have remained intact that day. The bridge collapsed also because it was negligently designed; for if it had been made stronger, it would have withstood the winds of the 7th of November.

In the case of the fish out of water, I can think of two simple ways of changing the world to save the fish's life, short of throwing it back in the water: The first is to allow its gills to function in the air. The second is to give it lungs. These give rise to solutions (1) and (2) above.

Alternatively, we can determine why a fish on land cannot survive by comparing it with something else that can survive. The crucial difference between the landed fish and a fish in the water is that the landed fish's gills are dry, and so aren't working properly. The crucial difference between the landed fish and ourselves is that the landed fish lacks the lungs we use to breathe.