In 1671, De Witt conceived of a life annuity as a weighted average of annuities certain where the weights were mortality probabilities (that sum to one), thereby producing the present value of a life annuity. Edmond Halley’s (of comet fame) representation of the life annuity dates to 1693, when he re-expressed a life annuity as the discounted value of each annual payment, multiplied by the probability of surviving long enough to receive the payment, and summed until there are no survivors. De Witt's approach was especially insightful and ahead of its time. In modern terminology, De Witt expressed the value of a life annuity as the expected value of a random variable.