But capital may be increased even without personal sacrifice; as for instance, by mere occupation, as of certain goods, not hitherto recognized as such. Thus, also, by the establishment of valuable relations, the advantages of which either become the common good of all; or which, because at the exclusive command of one individual, obtain value in exchange. The progress of civilization itself may increase the value of existing capital. Thus, for instance, a house, considered as capital, may double in value if a frequented street be opened in its neighborhood. To this category belong all improvements in the arts which enable existing capital to achieve more than it could before. The invention of the compass increased the value of the capital employed in the merchant marine to an extent that cannot be calculated.(298) The increase of capital effected by saving soon finds a limit unless such limit is widened by the progress of civilization.(299)(300) Chapter II. Co-Operation Of The Factors. Section XLVI. The Productive Coöperation Of The Three Factors. All economic production generally demands the coöperation of the three factors: external nature, labor and capital. But with the political economist, labor is the principal thing; and not merely because all capital presupposes labor, nor because every combination of the three factors is an act of labor; but, in general, because “the human mind’s idea of means and ends makes all goods goods for the first time.” (_Hufeland._) Leaving the free forces of nature, surrounded by which we live and work, out of consideration, and also the fact that all raw material is due to nature, land is the indispensable foundation of all economy. But how little can unassisted nature do to satisfy human wants! How much less to produce goods possessed of value in exchange! A virgin forest, for instance, sold in its natural state, has, indeed, value in exchange, but only because it is taken into account that it can be cleared, and that there are means of transportation already existing.(301) The greater part of the forces of nature are latent to nomads and nations of hunters. When labor develops, they are set free to assist it.(302) It is very seldom that any thing can be produced without capital. Even the poorest gatherer of wild berries needs a basket and must be clothed.(303) Were there no capital, every individual would have to begin at the very beginning every moment. Life would be possible only in a tropical climate. No man, since the days of Adam, has been able to labor, except on the condition that a considerable advance of capital had been made upon him. There is not a nail in all England, says Senior, which cannot directly or indirectly directly be traced back to savings made before the Norman conquest.(304) Section XLVII.