To make certain; to define or reduce to precision by moving obscurity or ambiguity. The divine law ascertains the truth.

To make certain, by trial, examination or experiment, so as to know what was before unknown; as, to ascertain the weight of a commodity, or the purity of a metal.

To make sure by previous measures. The ministry, in order to ascertain a majority in the house of lords, persuaded the queen to create twelve new peers.

To make certain or confident, followed by a pronoun; as, to ascertain us of the goodness of our work.

To fix; to establish with certainty; to render invariable, and not subject to will. The mildness and precision of their laws ascertained the rule and measure of taxation.