A tweak of God's knobs
…Imagine if the values of one or two of nature's fundamental constants were slightly different, say the strengths of forces that hold atoms together. One consequence might be that the Earth's oceans would regularly freeze. Water - essential for life - is unique in being lighter as a solid than as a liquid. So ice sheets float and form an insulating layer that stops the deeper waters freezing. If water was more conventional then the primordial oceans would never have stayed liquid for long enough for life to evolve. But then of course we would not be here to ponder our good fortune.
Maybe I'm missing the point, but I could never understand all the fuss about the anthropic principle: it seems so bleeding obvious to me, it hardly warrants comment, let alone controversy.