Augustine records this “pear incident” in his Confession to rationally and empirically demonstrate why human beings voluntarily sin. We love to sin; so we make conscious decision to sin. He recalls this one particular incident of his childhood when his friends and he stole pears not to eat but to throw them away. So, he argues that we sin not because we have to but we love to sin.

This is coherent with the Scripture where Apostle Paul asserts in Romans 7:14-20 ESV

(14) For we know that the law is spiritual, but I am of the flesh, sold under sin. (15) For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. (16) Now if I do what I do not want, I agree with the law, that it is good. (17) So now it is no longer I who do it, but sin that dwells within me. (18) For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. (19) For I do not do the good I want, but the evil I do not want is what I keep on doing. (20) Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.