He was arguably the most historically important person ever born in Nevada County, but ask someone on the street about Josiah Royce and you can expect to hear a quick "I don't know" or be met by a blank stare. The only trace of him within the Grass Valley city limits, the town of his birth, is a plaque in front of the Grass Valley Library on Mill Street.It reads: "Josiah Royce. Born in Grass Valley. Alumnus of the University of California. Renowned Harvard teacher and eminent American philosopher."Serendipitously, the library is located on the exact spot where Royce was …