כאבן, ומה הוא הסבה שהמים יתקשו כאבן, שבזה ג"כ יש דעות שיש חומר מקפיא ומקרר, ויש דעות שעקר טבע המים להיות במעמד הקפאון רק החום יתיך אותו ובסור החום ישובו אל טבעם: What causes water to freeze solid? Malbim mentions two theories which had been around since antiquity: (i) the existence of a substance that cools and freezes - a primum frigidum; (ii) that the principal nature of water is to be in the frozen state, the addition of heat [caloric] causing it to melt and the removal of heat causing it to return to its natural solid state.24 Whether cold, in the objective sense, should be regarded as a real quality or just an absence of heat was long an unresolved question. In his New Experiments and Observations touching Cold, Robert Hooke wrote: '...the dispute which is the primum frigidum is very well known ...some contending for the earth, others for water, others for the air...but all seeming to agree that there is some body or other that is of its own nature supremely cold and by participation of which all other bodies obtain that quality.'