The Spiral of Inquiry follows the natural pattern of questioning in humans into the vortex of inquiry that spirals inward to the primordial Truth that makes all inquiry possible. Arnold C. Harms finds the ability to question to be the most crucial to humanity, so that humans can be properly identified as homo interrogans, or Inquiring Man. This leads him to an examination of the process of questioning, beginning with a phenomenological inquiry into the language related to questioning. To illustrate the process of inquiry, Harms analyzes five representative types of formal inquiry: rational, scientific, historical, psycho-social, and religious. Through these styles, he demonstrates that all formal inquiries, when probed deeply enough, are drawn into the great spiral of inquiry, which leads inescapably to the primal Answer about the primordial Truth which makes all inquiry possible. The author identifies this central truth as the Cosmos with its universal order, without which there would be no inquiry at all. With this study, Harms clarifies much of the language surrounding the process of inquiry in humans.