Gordian knot
absurdity
ambiguity
ambivalence
antinomy
asymmetry
contradiction
crux
dilemma
disproportion
disproportionateness
enigma
equivocality
equivocation
heresy
heterodoxy
heterogeneity
hopelessness
impossibility
impossible
impossibleness
incoherence
incommensurability
incompatibility
inconceivability
incongruity
inconsistency
inconsonance
irony
irreconcilability
juxtaposition
knot
knotty point
koan
mystery
no chance
node
nodus
nonconformability
nonconformity
nonplus
oxymoron
perplexity
pons asinorum
poser
problem
puzzle
contradiction in terms
absurdities
anomaly
axiom
blunder
coincidence
conceit
discrepancy
exaggeration
fallacy
falsehood
metaphor
nonsense
novelty
perversion
resemblance
revelation
riddle