Art is, at best, an imperfect science. Know what I mean?
Like Science, Art is concerned with thinking up new things, trying them out, and seeing how you did.
This last bit is very important, for the artist who does not measure results is an unrepentant idealist.
Consequently, the artist who plans out every last detail may not be an artist at all; they may be a designer!
Somewhere between these extremes is "the middle ground" - a space populated by shades of grey. Or is it gray? I forget...