The initial plans and outline for this book, I and Thou, were put to paper more than 40 years before the eventual publication. Since publication, there have been a number of criticisms and questions that have come to light which need to be addressed and clarified.

The first question is concerned with the manner of I—Thou relationships between people and between other creatures, and what makes these relations different and distinct from one another. The true test of the depth of the I—Thou relation is the capability of the Thou to respond to the I. In plants, this is not possible in speech; animals, meanwhile, are capable of offering a conscious kind of response. Human beings actually desire this manner of animal response, as evidenced by the existence of tamed and trained animals which are designed and brought into existence for the purpose of responding to human ingenuity and control.

The realm of the spirit is more fraught with difficulty, however, which leads to the second question: How is the world of spirit to be communicated with and recognized as Thou when we cannot hear it respond to our outreaching search? First, a distinction needs to be made, for there is a division even in the realm of spirit: