Necessary knowledge (ʿilm daruri) arises without the recipient having to arrange and examine a formal argument. Inferential knowledge (ʿilm nazari) is reached through consideration, evidence, and reasoning.
When all the conditions of tawatur are met, it produces necessary knowledge: even an ordinary listener without formal training in argumentation may gain certainty from a properly transmitted account.
Daruri illustration: Publicly and independently transmitted sensory evidence leaves the hearer certain that an event occurred.
Nazari illustration: A researcher establishes a conclusion through several premises and an argument.
Both can concern true conviction; what differs is the route by which the knowledge is attained.