He says the president began to think seriously about the meaning of life after Willie died in eighteen sixty-two.

VOA: special.2009.02.09

And the more I went into it, the more I thought as I see something seriously wrong here with the way we think about animals and the way we treat animals.

于是，随着研究的深入，我所思考的也越来越多,我发现我们对于动物的认识,我们对待动物的方式,存在着严重的问题。

普林斯顿公开课 - 人性课程节选