Columbus and Paracelsus, for example, believed that the magnet was attracted by some point in the heavens, such as a magnetic star.

Gilbert himself tells of some of the beliefs that had been held by his predecessors, many of whom he declares "wilfully falsify." One of his first steps was to refute by experiment such assertions as that of Cardan, that "a wound by a magnetized needle was painless"; and also the assertion of Fracastoni that loadstone attracts silver; or that of Scalinger, that the diamond will attract iron; and the statement of Matthiolus that "iron rubbed with garlic is no longer attracted to the loadstone." Gilbert made extensive experiments to explain the dipping of the needle, which had been first noticed by William Norman.

His deduction as to this phenomenon led him to believe that this was also explained by the magnetic attraction of the earth, and to predict where the vertical dip would be found.

These deductions seem the more wonderful because at the time he made them the dip had just been discovered, and had not been studied except at London.

His theory of the dip was, therefore, a scientific prediction, based on a preconceived hypothesis.