Secular is whatever has reference to this life. Secular instruction is instruction respecting the concerns of this life. Secular subjects therefore are all subjects except religion. All the arts and sciences are secular knowledge. To say that secular means irreligious implies that all the arts and sciences are irreligious, and is very like saying that all professions except that of the law are illegal. […] To know the laws of the physical world, the properties of their own bodies and minds, the past history of their species, is as much a benefit to the Jew, the Mussulman, the Deist, the Atheist, as to the orthodox churchman; and it is as iniquitous to withhold it from them. Education provided by the public must be education for all, and to be education for all it must be purely secular education.

John Stuart Mill (1806-1873) English philosopher and economist

“Speech on Secular Education,” undelivered (1849)