Ray Kurzweil and his son, Ethan, are both Silicon Valley futurists — though they have different ways of tackling what they perceive is coming next. Ray Kurzweil, 65 years old, joined Google Inc. in December after spending nearly five decades pioneering everything from machines that can read text aloud to the blind to a music synthesizer that sounds like a real piano.

Among his theories, which aren’t universally accepted in the technology world, is the “Law of Accelerating Returns.” This states that technological progress increases exponentially, eventually allowing people to enhance their intelligence and live forever. He also envisions a future in which artificial intelligence surpasses human intelligence and spreads out across the universe, which he calls “the singularity.” […]