EN
We show that any quasi-arithmetic mean $A_{φ}$ and any non-quasi-arithmetic mean M (reasonably regular) are inconsistent in the sense that the only solutions f of both equations
$f(M(x,y)) = A_{φ}(f(x),f(y))$
and
$f(A_{φ}(x,y)) = M(f(x),f(y))$
are the constant ones.