Presumptions arise from what generally happens.

Explanation

(English-origin maxim.) Presumptions are drawn from the ordinary course of events — what usually happens in similar circumstances provides the basis for inferring what happened in the case at hand.

Where this applies

• A letter was mailed from the same city as the recipient — the court presumes it was delivered within a day or two because that's what ordinarily happens with local mail.
• A contract is signed by two businesspeople at a formal meeting — the court presumes both read it before signing, because that's what people generally do in business transactions.
• A store sells a product in its original sealed packaging — the court presumes the contents match the label, because manufacturers generally put the right product in the right package.