The reason people now say to tow the line is that it makes a kind of sense. Only in the hands of stale traditionalists does it mean what it used to mean, to be precise, like a soldier, in the observance of authority. To home in on had its intents and purposes in the days of homing pigeons and other such devices, but now we are much more inclined to get to the point. Taken out of historical context, intents and purposes, a sixteenth-century legal redundancy, makes little sense, for it says the same thing twice. It is therefore not surprising that it has been mistaken.
Intensive purposes sounds impressive.
It is not very meaningful, but no doubt it means more to most than intents and purposes. It draws its existence from intents and purposes, clearly, but in such a mangled form that it looks as if the corpse s skeleton had been rebuilt, and so it is perhaps appropriate to call it and like expressions, as I have already done, disinterred metaphors. Most disinterred metaphors have assumed the proportions of folklore. They reflect a common struggle with the language, felt by all speakers of the language. They are so frequent in their appearance that it is hard to imagine anyone being the first person to have used them.