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have half a notion to do something

 and have half a mind to do something
Fig. to have almost decided to do something, especially something unpleasant. I have half a mind to go off and leave you here. The cook had half a notion to serve cold chicken.
See also: half, have, notion

not have the foggiest notion

to not know anything at all about something not have the faintest idea I don't have the foggiest notion what that book is about.
See also: foggy, have, not, notion
References in classic literature ?
From this last speech I derived the notion that Miss Havisham, for some reason or no reason, had not taken him into her confidence as to her designing me for Estella; that he resented this, and felt a jealousy about it; or that he really did object to that scheme, and would have nothing to do with it.
And it must be noted that I say of our reason, and not of our imagination or of our senses: thus, for example, although we very clearly see the sun, we ought not therefore to determine that it is only of the size which our sense of sight presents; and we may very distinctly imagine the head of a lion joined to the body of a goat, without being therefore shut up to the conclusion that a chimaera exists; for it is not a dictate of reason that what we thus see or imagine is in reality existent; but it plainly tells us that all our ideas or notions contain in them some truth; for otherwise it could not be that God, who is wholly perfect and veracious, should have placed them in us.
Yet this singular and almost accidental character of his mission agrees with the divine sign which, according to our notions, is equally accidental and irrational, and is nevertheless accepted by him as the guiding principle of his life.
Had Mademoiselle Hennequin been an American girl, he would not have thought a second time of the emotion she had betrayed in regarding my beauties; but he had been taught to believe all French women managing and hypocritical; a notion that the experience of a young man in Paris would not be very likely to destroy.
Harvey had a notion that the east coast of his native land, from Mount Desert south, was populated chiefly by people who took their horses there in the summer and entertained in country-houses with hardwood floors and Vantine portieres.
Yes, it does give a notion," said Catherine warmly, "and that is, that you all drink a great deal more wine than I thought you did.
No, I know the notes of many birds, and I know many melodies by ear; but the music that I don't know at all, and have no notion about, delights me--affects me.
Will Meno tell him his own notion, which is probably not very different from that of Gorgias?
Would you like to give them such a melancholy notion of what goes on down here?
The traditional conception of cause and effect is one which modern science shows to be fundamentally erroneous, and requiring to be replaced by a quite different notion, that of LAWS OF CHANGE.
Asked next, if she had mentioned this notion of hers to any other person, Penelope answered, "I have not mentioned it, for Rosanna's sake.
And these were all the notions he had concerning that faculty of lying, so perfectly well understood, and so universally practised, among human creatures.
This gossiping familiarity shocked the captain's notions of rank and subordination, and nothing was so abhorrent to him as the community of pipe between master and man, and their mingling in chorus in the outlandish boat-songs.
Arthur is not what is commonly called a bad man: he has many good qualities; but he is a man without self-restraint or lofty aspirations, a lover of pleasure, given up to animal enjoyments: he is not a bad husband, but his notions of matrimonial duties and comforts are not my notions.
But to represent the Almighty as avenging the sins of the guilty on the innocent, was indecent, if not blasphemous, as it was to represent him acting against the first principles of natural justice, and against the original notions of right and wrong, which he himself had implanted in our minds; by which we were to judge not only in all matters which were not revealed, but even of the truth of revelation itself.