cannot but

• cannot help but, can't help but
• can't but

cannot but (third-person singular simple present cannot but, no present participle, simple past could not but, no past participle)

1. To have to; to cannot help; to be unable to do otherwise than.
   • 1789, Benjamin Franklin, “Letter to Noah Webster, December 26, 1789”, in E. Sargent, editor, The select works of Benjamin Franklin‎, published 1855, page 498:

     I cannot but applaud your zeal for preserving the purity of our language, both in its expressions and pronunciation, and in correcting the popular errors several of our States are continually falling into with respect to both.

• Merriam-Webster Collegiate Dictionary
• Concise E-C Dictionary