'The numerous chapters are highly comprehensive. Even for experienced observers with extended capabilities, the book offers sufficient material for weeks or even months of pertinent activity and thus for gaining new experience. The mathematical approaches indicate that laws of nature are involved here. From his treatment, the curiosity and diligence of the author are obvious as he observes the world with extended senses, both alone and with the assistance of other sensitive persons.However, even for non-sensitive persons, the book has something special to offer, that is, an understanding for the possibility of discovering hitherto unknown aspects of one's environment with good sensors and thus deriving new information for our view of the world.In great detail, J. Keen considers mental paths, Psilines, and smugglers' Psi lines, which are perceivable and traceable connecting lines between two locations, similar to the Psi-tracks investigated in Sweden.The consequences of this and of the other experiments are so overwhelming that one must arrive at completely new ways of thinking in analogy with The Mind's Interaction with the Laws of Physics and Cosmology.'- Friedrich H. Balck, www.biosensor-physik.de, 2018'Keen's book is a highly ambitious and serious inquiry that is most likely intended for the scholarly or serious dowsers. And Keen presents copious graphs, illustrations, and photographs to facilitate what would otherwise be very difficult subject matter to grasp. Keen offers a deep (and in my view fascinating) exploration into different kinds of subtle energies, which range from lines across the landscape, auras (for both living and non-living forms), vorticular energies, "psi-lines," and others. Keen is eager to quantify everything he can, often in surprising ways. Many of his findings are counterintuitive, as well as intriguing. His detailed charts and illustrations demonstrate how various properties vary with distance or time. Also, Keen's attempts to use equations to ascertain the relationships of various aspects of subtle energy observations are impressive. Almost needless to say, Keen is especially interested in mathematical constants and series, such as phi and Fibonacci's sequence, that mystics and occultists have been fascinated with for centuries.'George Williams, Journal of the Society for Scientific Exploration, Volume 33, Issue 2, 2019
