Now the ideality of time is established, according to Schopenhauer, by what is known in mechanics as the law of inertia. "For what," he asks in the "Parerga," "does this law teach? Simply, that time alone cannot produce any physical action, that alone and in itself it alters nothing either in the repose or movement of a body. Were it either accidentally or otherwise inherent in things themselves, it would follow that its duration or brevity would affect them in a certain measure. But it does nothing of the sort; time passes over all things without leaving the slightest trace, for they are acted upon only by the causes that unroll themselves _in_ time, but in no sense by time itself. When, therefore, a body is withdrawn from chemical action, as the mammoth in the ice fields, the fly in amber, and the Egyptian antiquities in their closed necropoli, thousands of years may pass and leave them unaffected. Indeed," he adds elsewhere, "the living toads found in limestone lead to the conclusion that even animal life may be suspended for thousands of years, provided this suspension is begun in the dormant period and maintained by special circumstances." The "London Times," 21st September, 1840, contains a notice to the effect that, at a lecture delivered by Mr. Pettigrew, at the Literary and Scientific Institute, the lecturer showed some grains of wheat which Sir G. Wilkenson had found in a grave at Thebes, where they must have lain for three thousand years. They were found in an hermetically sealed vase. Mr. Pettigrew had sowed twelve grains, and obtained a plant which grew five feet high, and the seeds of which were then quite ripe. Many other instances are given of this absolute inactivity; for example, let a body once be put in motion, that motion is never arrested or diminished by any lapse of time; it would be never ending were it not for the reaction of physical causes. In the same manner a body in repose would remain so eternally did not physical causes put it in motion. It follows, therefore, that time is not a real existence, but only a condition of thought, or purely ideal.