What is so important about Sol LeWitt's Cube without a Cube sculpture?

Sol LeWitt had many variations of the cube sculpture.

What is always most important to remember about Sol LeWitt is HE IS THE FATHER OF CONCEPTUAL ART.

Which means he himself DID NOT MANUALLY create the sculpture. Instead, he created THE IDEA of the sculpture.

It's like when you think to yourself..."I'm going to draw a picture of my cat."

And you draw a picture of your cat and it looks like NOTHING what you had in mind.

Sol saw there was a difference between the idea of drawing your cat and the execution of drawing your cat.

So Sol began to focus on his ideas - rather than the execution.

(Note: Sol was trained in painting, drawing, and design, however he focused most of his intentions on his concept. Other than early concepts, Sol never physically executed his ideas. Trained draftsmen carry out the physical act of sculpting, drawing, or painting.)

So the INSTRUCTIONS are what's important about Sol LeWitt's "Cube without a Cube."

Now, if you're asking on a more philosophical level - that would take a much longer time to answer, but I hope this helped!