unsolved problems
- mysteriesUnexplained phenomena or events
- enigmasInexplicable mysteries
- puzzlesProblems designed to challenge
- riddlesPuzzling questions or teasers
- cold casesUnsolved, inactive investigations
clues · detective · investigation · conjectures · theorems · missing · unknown · baffling · perplexing · stumped · breakthrough · evidence · leads · dead ends · ciphers · codes · questions · hypotheses
problem existence
unsolved problemsnon-issues
Matters requiring no attention
smooth sailing · no problem · clear path · clear sailing · clean slates
epistemic clarity
unsolved problemsknown quantities
Established, measurable factors
certainties · closed questions · common knowledge · received wisdom