Thus we see it is only through attention that the faculty of association becomes a property advantageous to the organism, and attention is nothing but the faculty of the will to determine the emergence, degree of clearness, duration and extinction of presentations in consciousness. The stronger the will, so much the more completely can we adapt the whole organism to a given presentation, so much the more can we obtain sense impressions which serve to enhance this presentation, so much the more can we by association induce memory-images, which complete and rectify the presentation, so much the more definitely can we suppress the presentations which disturb it or are foreign to it; in a word, so much the more exhaustive and correct will our knowledge be of phenomena and their true connection. Culture and command over the powers of nature are solely the result of attention; all errors, all superstition, the consequence of defective attention. False ideas of the connection between phenomena arise through defective observation of them, and will be rectified by a more exact observation. Now, to observe means nothing else than to convey deliberately determined sense-impressions to the brain, and thereby raise a group of presentations to such clearness and intensity that it can acquire preponderance in consciousness, arouse through association its allied memory-images, and suppress such as are incompatible with itself. Observation, which lies at the root of all progress, is thus the adaptation through attention of the sense-organs and their centres of perception to a presentation or group of presentations predominating in consciousness. A state of attention allows no obscurity to persist in consciousness. For either the will strengthens every rising presentation to full clearness and distinctness, or, if it cannot do this, it extinguishes the idea completely. The consciousness of a healthy, strong-minded, and consequently attentive man, resembles a room in the full light of day, in which the eye sees all objects distinctly, in which all outlines are sharp, and wherein no indefinite shadows are floating.