How to spot it in the stimulus
1
One premise supporting one conclusion.
2
The conclusion introduces a new idea the premise never mentioned.
3
That jump from the premise's idea to the new idea is the gap.
The assumption
True for every P → C argument: the assumption is the link that connects the premise to the conclusion.
P → C
The argument treats the premise as sufficient for the conclusion.
To find it
Name the premise, name the conclusion, then link them. Whatever bridges P to C is the assumption.
Quick check: premise = sufficient, conclusion = necessary.
Worked examples
Volcano
PremiseThe volcano erupts.
ConclusionThe plants die.
Assumptionvolcano erupts → plants die
Stars
PremiseTwo stars collide.
ConclusionNew planets form.
Assumptiontwo stars collide → new planets
Cave
PremisePaintings of men and animals.
ConclusionServed a religious purpose.
Assumptionpaintings of men and animals → serve a religious purpose