If a number is divisible by 10, it is divisible by 5: the consequent follows by necessity. If Zayd visits school, Bakr buys a pen: no intrinsic necessity is established. The decisive test is not whether both clauses happen to be true but whether the antecedent makes the consequent follow.
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Necessary versus coincidental at a glance
Conditional Propositions: Connected and Disjunctive Forms
If a number is divisible by 10, it is divisible by 5: the consequent follows by necessity. If Zayd visits school, Bakr buys a pen: no intrinsic necessity is established. The decisive test is not whether both clauses happen to be true but whether the antecedent makes the consequent follow.