Everything you see is really just patches of color, not objects

Ruskin's foundational claim is a perceptual one: the eye, in strict physiological terms, receives nothing but flat patches of variously colored and shaded light. The perception of solid form, depth, and recognizable objects is something the mind adds through learned interpretation, not something the eye directly registers. He insists beginning artists must consciously unlearn this automatic interpretation to draw what is actually in front of them rather than what their mind assumes should be there.

This is why, in his account, untrained people draw a face as a set of symbols — two dots for eyes, a line for a mouth — rather than the specific arrangement of light and shadow actually visible on a particular face. The habitual mental shortcut that lets us instantly recognize objects in daily life becomes a liability at the drawing desk, where accuracy requires temporarily suspending that shortcut and attending to raw visual patches instead.

Takeaway: to draw what's really there, you first have to stop seeing objects and start seeing light and shadow.