dysrationalia
rocks in one's head
not the sharpest knife in the drawer
not the sharpest tool in the shed
not the sharpest tool in the box
stupid
weak
unintelligent
simple
simpleton
acognitive
gormless
incompetent
vacancy
light-witted
feeblemindedness
sophomania
dimwit
insensitive
simplicity
dickheadedness
noncognition
childish
subintellectual
unintelligence
subnormal
subnormality
acataleptic
underbrained
incognizability
imperception
whifty
simple-minded
folly
imbecility
unskillfulness
simple-mindedly
blinded
nonintelligence
disorderly
indiscernible
unperceivingness
not with it
inconsideration
inapproachability
simple-mindedness
incompossibility
feeble-minded
stupidass
fool