Of Two Minds - edit3

[Magpie]

Of Two Minds  - good title


I don’t believe some evil other hand
built those dark Monticello passages
which then permitted Thomas Jefferson
to visit its slave quarters secretly. - good start - sets up the poem nicely
No, he designed and utilized, and knew...
but not, perhaps, each hour of each day. - this line seems awkward in context with the above line. Although you are implying that he didn't utilize them all the time, the line above ends on 'and knew...' so it feels like it's implying that he didn't know about them each hour of the day. 

Just as that gifted polymath believed
his god an immanent but unconcerned - good choice not to capitalise god
endowing, cool, impersonal Creator–   - in my reckoning (and perhaps accent) this line has eleven syllables as opposed to ten in all the other lines. It makes it feel overly long - is 'cool' necessary? - also should 'Creator' be capitalised? it gives more importance to a deity who has just been described as unconcerned and impersonal 
most days, and while he wrote of human rights.
But other times he trembled when he thought
with yearly mounting dread that God is just. - good ending and choice to this time capitalise 'God' - gives the contrast with the previous thought. Also, tiny nit 'just' repeated twice in this stanza - no big deal though

Good poem exploring a belief in an 'unconcerned creator' versus a God that sits in judgment. Enjoyed reading and looking up information in relation to it.