start a fresh hare

Like a huntsman who, for the sake of a better run, should outrace his quarry, or who, seeing that the dogs were close upon the hare, should, in order to prolong the chase, start a fresh hare, kept till then snug at his saddle-bow, so Hume, in the excitement of metaphysical pursuit, instead of stopping to gather up whatever verified affirmations came his way, would prefer to follow any new negation that he espied, or, if momentarily accepting any affirmation as established, would proceed forthwith to affirm its direct opposite with the view of neutralising both.