We present a macroscopic treatment that clarifies the role of phonons in the wetting of a solid by an ideal liquid, such as liquid 4He. We show that in the equation for the wetting temperature the phonon contribution cancels exactly. Therefore, a pure phonon mechanism always results in wetting, and other mechanisms determine whether wetting or non-wetting occurs. The importance of ripplon excitations for the wetting phenomenon is discussed. © 1997 Published by Elsevier Science B.V.