It is an odd thing that we light and bless a fire. It all sounds rather pagan like turning toward the four winds and praying to the elements. But there are practical as well as spiritually orthodox symbolic things going on here.
Much of the practical is lost on moderns particularly in westernized countries. Do you need warmth? Turn the thermostat up. Do you need light? Flip the switch. Do you need help hearing? Speak into the microphone. For most of the history of mankind and indeed for most people alive today this is not always a ready remedy. Things are much more basic outside of our little bubble of existence. Is it dark? Go to bed or light a candle. Are you cold? Bundle up together under a blanket and light a fire.
The candles at Mass have nice symbolic meanings which have been reported on here in the past, but they are also immensely practical: They provide light so we can see to pray the Mass, proclaim the readings and etc.
So back to the Easter fire. Fire is used for warmth, light, in preparations for nourishment, for sanitizing and purifying, and even protection. (Who doesn’t feel better sticking closer to the fire at a campout after a good ghost story?) The symbolism is clear then: Fire represents Jesus. This is the light that we carry into the Church, the light that destroys the darkness, Jesus, the light of the world and gives life and warmth. This is what we are to become and that night so we do as we each carry our light of Christ – “a light divided yet undimmed.”
The prayer over the fire points mightily to all of the symbolism going on. “We share the light of your glory through your Son, the light of the world. . . inflame us with new hope . . . purify our minds . . . bring us to the feast of eternal light.”
Finally, in some ways it undoubtedly has some roots in paganism. According to the OSV Catholic Encyclopedia, though the lighting and blessing of an Easter fire seems to have been present since the beginning of the liturgical celebrations of Easter, “in a custom attributed to St. Patrick, the Celtic Church began with the lighting of an outdoor fire, ‘baptizing’ the practice of local pagan priests, the warmth of the fire no doubt evoking the sense of the ‘quickening of life’ accomplished definitively for the Christian by the resurrection of Christ.”
Some Christians strongly object to the “baptizing” of anything pagan and using it in the worship of the one true God. As G. K. Chesterton once pointed out walking on two legs should be done away with also because they were used in the worship of the pagan Gods. The same would go with singing, the raising of hands, standing, sitting, the use of buildings, the non-use of buildings, silence and making noise, the use of incense and the non-use of incense. It all becomes rather convoluted. But if these practices bring us closer to God, make us understand His way better symbolically, help us relate better by using those things that are so part of the human experience, then it would be silly not to make use of them.