can't but

past couldn't but

1. alternativeno past participleno present participleAlternative form of cannot but.

   […] the man of letters can't but love the place which has been inhabited by so many of his brethren, […]

   1848 November – 1850 December, William Makepeace Thackeray, “The Knights of the Temple”, in The History of Pendennis. […], volume I, London: Bradbury and Evans, […], published 1849, →OCLC, page 290

   2 more examples

   18th c, Jonathan Swift, Alexander Pope (later lines), Imitation of Horace, 1852, Charles Knight (collator), Half-hours with the Best Authors, Volume 4, page 188, But here a grievance seems to lie, / All this is mine but till I die; / I can't but think 'twould sound more clever, / To me and to my heirs forever.

   I'd weave through the throng — scanning for empties to return while flirting, sniffing out kids smoking grass and sharing smokes with Ivor and Carl on the door. With a name like Carl you can imagine a six-foot tall and wide bouncer, but Ivor...I couldn't but help to think of the name as belonging to a skinny Welshman getting sand kicked into his face. His name didn't do him justice — this guy was almost as big as Carl and probably faster with his fists.

   2004, David W. Scott, The Disillusioned: A Story of Our Times, Fraser Books, →ISBN, page 204