While some find many instances of symbolism is Synge's play, from the bed symbolizing the concept of marriage in Mayo to marriage itself symbolizing confinement to Mayo village life, it may be argued that the most significant (i.e., important and meaningful) symbols are those that are religious and cultural.
Mayo, Ireland, was virtually exclusively (if not in fact exclusively) Catholic during the time in which Synge set his highly controversial play. Yet, the oft mentioned Father Reilly is never present, only oft mentioned. In fact, Father Reilly has no place in the Cast List as he takes no human form. The good Father may be said to be a religious symbol of Mayo's conflicting attitude toward religion as the villagers give voice-service to the beliefs, rites and sacraments yet live by rules of superstition and village anarchy, both of which are antithetical to the invitation to love-regulated and well-reasoned life as put forth in the New Testament (though how well the invitation has been historically understood and acted upon presents an opening for great debate). The good Father Reilly is purely symbolic in this play as we are continually waiting for him to become an actuality, just as Shawn and Pegeen are waiting for him:
SHAWN. Aren't we after making a good bargain, the way we're only waiting these days on Father Reilly's dispensation from the bishops, or the Court of Rome?
Mayo was also a source of cultural symbolism to Irish audiences of the day, particularly in light of the Irish National Theatre movement. Mayo symbolized the purity and honest goodness of the Irish peasant people and was tightly tied up in what might be called the Irish pastoral vision in which country life and people symbolize simple goodness, honesty, and dedication to useful work. In other words, Mayo symbolized the Irish concept of the Wordsworthian Romantic pastoral ideal as might be exemplified by Wordsworth's poem, The Ruined Cottage. That the villagers in Synge's play could alternately interrogate, accept, venerate, condemn, punish, and lament the loss of one wholly unknown and reputedly a murdering scoundrel was an outrage to this Irish idyllic pastoral symbol. That such a stranger and villain could command--or even think he could command--the presence of hundreds, or even thousands, of Mayo maidens half clad and ready to throw their maidenhood at Christy's feet was another outrage to the symbol of Mayo as the pastoral ideal.
CHRISTY. It's Pegeen I'm seeking only, and what'd I care if you brought me a drift of chosen females, standing in their shifts itself, maybe, from this place to the Eastern World? [Paraphrase: Pegeen is the only woman I want, and what would I care if you brought me a long line of the best females--maybe standing in only their nightgowns--[that extended] from Mayo to the countries of the East?]
[See "The Playboy Riots," Dr. Mary Trotter, Indiana University-Purdue University Indianapolis/Miami University.]