The Ghost of Gould

Stephen Jay Gould died a number of years ago, but his legacy lives on.
In the previous post, Monk has asked that I consider three known facts, and believes that if I should agree these facts are true, then I must accept evolution as a scientific fact.
What Monk has done is to provide a variation on the reasoning proposed by Gould - a thinking that sounds logical, but is overwhelmingly flawed.
The argument Gould makes starts off with 3 postulates: 1. animals produce more offspring than they need to (many will die off), 2. offspring will vary in appearance to each other, and 3. the environment will select for the offspring that are best fit. Gould states that these 3 postulates are obviously true (it's a matter of common sense), and therefore evolution is a fact of life.
But unfortunately for Stephen, he made an error in logic.
Can anyone tell me what that error is?