Presumption
Etymology
From Latin "praesumere" (to take beforehand, to anticipate) — "prae-" (before) plus "sumere" (to take). A presumption is something taken as settled in advance; the same root also gave "presumption" its secondary sense of overstepping, taking more than one’s due.
noun · /prih-ZUMP-shun/
A belief taken as true by default until sufficient reason arises to abandon it.
What it names
A handle for a starting position that sets who bears the burden of proof — the claim that stands unless someone knocks it down.
Example
The presumption of innocence means the state must prove guilt — the accused need prove nothing.
Related idea
Distinguish it from a plain assumption: an assumption is simply taken for granted, while a presumption is a considered default that explicitly puts the burden of proof on whoever would overturn it. Presumptions are the load-bearing defaults of law and fair argument.
noun · /prih-ZUMP-shun/
Behavior that oversteps what is proper; arrogant overconfidence or audacity.
What it names
the overstepping of proper bounds
Example
It was sheer presumption to answer in the host’s place.
Related idea
From ‘taking’ too much upon oneself; compare arrogance, entitlement.