No offence to Hugh MacLennan, but you don't even have to know or understand any deep philosophy that's being espoused, you can just have the feeling of those words together, and that you know them and can sing along with that melody with your fist up in the air. It's a wild vehicle for sentiment, because it's so powerful on the musical front.
The important point is that since the origin of life belongs in the category of at-least-once phenomena, time is on its side. However improbable we regard this event, or any of the steps which it involves, given enough time it will almost certainly happen at least once. And for life as we know it, with its capacity for growth and reproduction, once may be enough.