based on the qualities of someone or something, or on the facts of a situation.
The mayor makes job appointments only on the merits.
Usage notes: used especially in legal decisions:
His pardon was granted solely on the merits.
on the merits
According to or based on facts or qualities essential to a person or situation, as opposed to circumstantial or technical details. Usually used in reference to a decision by a judge in a legal case. The defense filed a motion for dismissal based on the prosecution's failure to include the new evidence in the discovery phase, but the judged ruled that the case would be heard on the merits.