I’ve seen this attributed to Plato, as well. But Michael Noyes, the artist who did this piece, said the following:

“Philo of Alexandria was a first century Jewish philosopher. The colors of the large letters are those of the surface of the Earth, suggesting the necessity to be kind to EVERYONE we meet.”

Interestingly, some believe that Philo was actually the founder of Christianity. That’s because his philosophy apparently was a combination of Jewish theological ideas and those present in the Greey mystery religions.

When combined, some say these concepts would appear much like Christianity. It is possible, they say, that the followers of Jesus seized upon Philo’s precepts and incorporated them into the letters that became the New Testament.