If I understand FF correctly, intellect is the ability to calculate the effect of water running into a bath-tub at one rate and out at another; intelligence is the mind-power to reason that this is a waste of water; Common (or Good, if you really must) Sense tells you to put the plug in.

(Actually, I do have some sympathy with FF's dislike of Common Sense. As wseiber suggests, it isn't really so very common and, when it does occur, it isn't always sense. Common sense told many good people, for many centuries, that the earth is flat.