Blake was at least a little crazy, as under-appreciated or over-praised geniuses often are. Nevertheless, he was also a wise man because of his vision, because of what he saw when he looked at a tree. Unlike the fool who doesn't even notice the tree or only sees its utility as a source of shade or a landmark on his route to work, Blake saw angels of light glowing in the negative space between leaf and branch.
Rather than mere biology narrowing matter down to descriptive labels that dismiss the miracle of a particular tree in a particular season in a particular relationship to a specific forest, Blake saw the wondrous creation of an inspired artist and was moved to awe and worship.
Because I am largely a fool, that is, a dullard, half asleep, too preoccupied with burdens piled on my back by a culture infatuated with productivity and wealth rather than truth and beauty, I barely see, rarely worship, am mostly incapable of wonder or awe. So I can not adequately describe what a wise man sees.
My appreciation of this bold statement feels like a divine invitation to wipe the scales from my eyes, as I am graced to notice them, and keep expecting to see a revelation of incarnation in the trees that are burning to declare God's glory.