ad fontes

Etymology
+, accusative plural form of = literally, “to the springs or sources”; probably drawn from Psalm XLII, verse 1 of the Latin Vulgate by Spanish humanists.

Phrase

 * 1)  Go to the sources: An expression emphasizing the importance of conducting fundamental research and of consulting primary sources.

Usage notes

 * A motto of Renaissance humanists. Similarly, the Protestant Reformation called for the return to the Bible as the primary source of Christian faith. The idea in both cases was that sound knowledge depends on the earliest and most fundamental sources.