In writing THE PLAYBOY OF THE WESTERN WORLD, as in my other plays, I have used one or two words only that I have not heard among the country people of Ireland, or spoken in my own nursery before I could read the newspapers.... On the stage one must have reality, and one must have joy; (Preface, Synge)

As the quote from Synge's Preface to the play indicates, first and foremost, Synge was trying to reveal a genuine, sincere, authentic look into the society of West Ireland, an area held to be unspoiled by big city ideas and to still hold the simple poetry of early Irish life. Since Synge renounced his religious beliefs after reading Darwin at a young age, there is a conspicuous dearth of direct religious reference in The Playboy. You can see from the character list that there is no vicar: Father Reilly is not a present character, though repeatedly alluded to. We may infer that Synge had no intention to overtly address the Catholic religion of the region, though he did expose the social impact of their religion.

SHAWN — [in horrified confusion.] — I would and welcome, Michael James, but I'm afeard of Father Reilly; and what at all would the Holy Father and the Cardinals of Rome be saying if they heard I did the like of that?
[...]
SHAWN — [with plaintive despair.] — I'm afeard of Father Reilly, I'm saying. Let you not be tempting me, and we near married itself.

Synge's primary point related to society was to reveal the poetic nature of their language and to show the "imagination" of the people, imagination that drives their thoughts and actions and colors their understanding of the world. When the play was first staged, Irish audiences were outraged by it as was witnessed by the fist fights, walkouts,and regaling boos resounding throughout the theater. These audiences were incensed at Synge's representation of West people. Synge, on the other hand, found their "raw" life, thought, and language liberating and exemplifying of something higher and purer than that which existed in the jaded, dulled, homogenized cities.

It's harder to understand Synge's purpose in the exposure he gives to religion. The mention of God is in the vein of a metaphorical metaphysical umbrella that covers the characters' every waking moment and thought, yet the meaning of this pervasive awareness and presenceof religion is never made clear:

MICHAEL -- Well, God bless you, Christy, and a good rest till we meet again when the sun'll be rising to the noon of day.

CHRISTY -- God bless you all.

MEN -- God bless you.

CHRISTY -- ... God bless you, and would there be any offence if I was asking are you single now?

CHRISTY -- ...  poaching rabbits on hills, for I was a devil to poach, God forgive me,

WIDOW QUIN -- ... (To Christy.) God save you, mister!

CHRISTY -- [shyly.] — God save you kindly.

They have a village priest, Father Reilly, who is mentioned nearly as much as any character, yet we never see him or hear from him directly. It is always the shadow of Reilly that sways a character's speech and feelings and always the promise or threat of Reilly's displeasure or blessing that motivates what thoughts the impulsive, emotively reactionary characters have. From this we may infer that Synge is capitalizing upon the native religious persuasions of people in West Ireland in order to dramatize and expose his own belief system, one that has rejected religion.