According to tradition, St Patrick banished all snakes from Ireland. But it is thought that at least since the end of the last glacial period in about 9700 BCE, Ireland had no snakes. What is being conveyed or connoted in this tradition?
It is tradition that tells us that St. Patrick banished all the snakes out of Ireland. The fact is that Ireland never had any snakes to be banished! So what is this legend trying to tell us? St. Patrick rid Ireland of the serpentine snake of paganism to say the least.
No Snakes in Ireland
The St. Patrick mythology includes the claim that he banished snakes from Ireland.
It's true no snakes exist on the island today, Freeman said. But they never did.
Ireland, after all, is surrounded by icy ocean waters—much too cold to allow snakes to migrate from Britain or anywhere else. National Geographic News
So what is this legend trying to convey to us? The snakes could be a metaphor for something else. This metaphor could be symbolized as paganism, evil, or the Devil. You decide?
Since snakes often represent evil in literature, "when Patrick drives the snakes out of Ireland, it is symbolically saying he drove the old, evil, pagan ways out of Ireland [and] brought in a new age," Freeman said. - National Geographic News
This metaphor could be demons?
But what if the snakes were actually metaphors for evil spirits? I believe this was the case – in the Gospels Our Lord uses snakes as a metaphor for demons when He tells the apostles that when they will evangelize people and bring them to Christianity – they will walk among the nastiest of serpents and yet they will be unharmed because they have His protection.
What if St Patrick was actually an exorcist who exorcised Ireland of ‘snakes’ or demons? If indeed it was the case then St Patrick was genuinely heroic, the real snakes that slither through the grass can only harm us physically, but an evil spirit that tempts us to do harm to others and ourselves to the point where we corrupt our souls can mean we may lose our souls for all eternity, a point made by Our Lord when He warns us not to be afraid of they who will kill our corporal fleshy body, but they who will kill our souls. - "Did St. Patrick really banish snakes from Ireland? The real story could be more darker."
As a Catholic Bishop St. Patrick definitely had the authority to be an exorcist in all of Ireland. It is most probable the snakes symbolized evil and paganism as different side of a coin. Just do not tell the Leprechauns I said that.
Pagans: The Metaphorical Snakes
So unless St. Patrick couldn't tell a snake from a lizard, where does the legend come from?
Scholars suggest the tale is allegorical. Serpents are symbols of evil in the Judeo-Christian tradition—the Bible, for example, portrays a snake as the hissing agent of Adam and Eve's fall from grace.
The animals were also linked to heathen practices—so St. Patrick's dramatic act of snake eradication can be seen as a metaphor for his Christianizing influence. - Did St. Patrick Really Drive Snakes Out of Ireland?