4. _This classification of goods is abstract, in that it is a classification, not of concrete goods, but of qualities shared in some degree by nearly all goods._ Most goods unite in some degree both characters, but in varying measure. This is, therefore, a continuity classification, the varying classes of goods grading from those whose durableness is zero (just at the moment of consumption) to those most durable, which yield an endless series of uses or products. Yet the classification is practical, corresponding as it does with thoughts which men have in the use of goods. By repairs and other methods goods become, and are looked upon as, durable sources of a series of uses. It is to be noted further that the enjoyable goods pass over into psychic income, that is, they are the stream of objective utilities that is each moment detaching itself as income from the great mass of wealth. The durable goods are those utilities which for the time remain, not yet ripened or ready to be converted into psychic income. § II. CONDITIONS OF ECONOMIC WEALTH [Sidenote: Income as affected by climatic conditions] 1. _The bounty and variety of the natural supply of indirect goods in the material world are the prime conditions of a bountiful income to society._ The effect of climate on the supply of goods available for man is complex. Climate is itself a direct source of gratification. As temperature must be adjusted to man's need, climate satisfies wants directly. Health, energy, the beauty of noonday woods and of sunlit clouds are conditioned on the favor of nature. Climate affects, further, the supply of material economic goods. All the earlier civilizations arose in warmer countries. But, after man had gained a certain mastery over the obstacles of nature, he was able to soften the harsher features of climate, and with better shelter and clothing, with better stocks of winter food and fuel, the more favorable features of the temperate zone could be utilized. So civilization moved northward from Egypt and India to Greece and Rome, to northern Europe and America. [Sidenote: By natural resources] Soil conditions for vegetable life determine first the amount and kind of animal life. Animal life from one point of view is a parasite, living on the vegetable; it is only the vegetable that has power to assimilate most inorganic compounds. Water being a need of plant life, the amount of rainfall is one of the most important conditions of industry. Man, therefore, depends on the resources of the soil directly or indirectly; a fertile soil furnishes him either directly a supply of vegetable food, or indirectly a supply of animal food. Natural supplies of metals, of coal, and of timber are important consumption goods, but they are also indirectly the condition for a vast variety of other goods. The industry that could exist without iron, copper, and coal would be of a very low grade. [Sidenote: By flora and fauna]