Another light: Painting's phenomenal opticality

For Clement Greenberg, only painting free of any representational or illusionistic vestige was truly 'optical'. All other painting, even non-representational painting which still suggested volume or depth, he regarded to be 'tactile' Greenberg's agenda in making this distinction was significantly partisan, and the cause he championed is now a matter of art history. It's easy just to say now that every painting ever painted is visually perceived as a result of the light reflected from its surface: to that extent then, can't we say - contra Greenberg - that all painting is optical?