"The Mind Is an Enchanting Thing" takes the time to remind us what kind of knowledge the mind is capable of getting its hands on (if a mind has hands) -- from learned knowledge (like learning to play the piano or writing music) to the more unconscious, natural stuff (like memories and our senses). Moore seems to think the mind is like a sponge, sopping up whatever it comes in contact with. If knowledge is power, this poem suggests that the smarties will take over the world. But we already knew that anyway.
There is no actual cheerleading for knowledge in this poem—only for the mind's ability to gain knowledge.
Only because the mind can acquire knowledge does it have any power. Otherwise it's just a pile of gray gunk between our ears.