In John O'Donohue's book "Divine Beauty: The Invisible Embrace," the phrase 'without a shadow of a doubt' is explored through a poetic lens. The author suggests that doubt comes as a shadow, indicating an obstruction of clarity or certainty. This imagery emphasizes how doubt complicates our understanding and perception.

Interestingly, O'Donohue argues that this very doubt also contributes to greater illumination. While it signifies a lack of confidence, doubt can lead to deeper insight and understanding, as it forces us to confront and reflect on our beliefs. Thus, the presence of doubt can enhance our perception rather than diminish it.