[ohgodthecat]

No because then you wouldn't be able to arrive at a fixed solution there would be 9 solutions with 0 clues.

[SatvikBeri]

In a 1x1 grid you would only use one digit, not 9. A 1x1 grid requires 0 clues, a 2x2 requires 1 clue.

[its_so_on]

(tongue in cheek) right, a 1x1 grid requires 0 clues, it has only a single digit as its solution; that digit is -- [its_so_on looks left, cut to SatvikBeri]

[cperciva]

That digit is a 1, since for an NxN grid the values are 1 through N.

[pbhjpbhj]

I'm not sure what the "Rules of Sudoku" say but I assumed any single symbol of the solvers choosing would do.