Felix Adler 
Essentials of Spirituality [PDF ebook] 

The spiritual life depends on self-recollection and detachment from the rush of life; it depends on facing frankly the thought of death; it is signalized, especially, by the identification of self with others, even of the guiltless with the guilty. Spirituality is sometimes spoken of as if it were a kind of moral luxury, a work of supererogation, a token of fastidiousness and over-refinement. It is nothing of the sort. Spirituality is simply morality carried to its farthest bounds; it is not an airy bauble of the fancy, it is of "the tough fibre of the human heart." Felix Adler (1884 – 1963) was an accomplished American screenwriter whose career spanned over 30 years. He is best known for his work with the Three Stooges.