You can't assume a goddamned thing in the Navy.
This line becomes Captain Queeg's catchphrase. It is first used when Queeg reprimands Burt Gorton for not giving him a more complete estimation of the difficulty involved in recovering a target after the towline-cutting incident. Queeg always uses this line when reassigning the blame for incidents in which he was at fault. Later, after two people present evidence that the steward's mates had eaten the strawberries, Queeg again falls back on this sentiment, urging the search for a key to go on. In that instance, the line is proof of Queeg's stubborn desire to reenact an earlier success in which a key was found.