Nor can any effectual inferiority of service be claimed, simply because the productive power of one branch of business is, measured by the duration of its results, greater than another.(325) What is more perishable than a loaf of bread bought for dinner? What more imperishable than the _monumentum ære perennius_ of a Horace? The labor expended on persons and on relations (_Verhältnissen_) is, both as to the extent and duration of its results, much less capable of being estimated than any other; but its capacity of accumulation and its power of propagation are greater than any other. It is in the domain of the “immaterial,” that man is most “creative.” (_Lueder._)(326) Finally, neither should the greater indispensableness of the more material branches of business be too generally asserted. Agriculture produces grain which is indispensable, and tobacco which is not; industry, cloth, as well as lace; commerce draws from the same part of the world rhubarb and edible bird’s-nests; and so, to _services_ belong the indispensable ones of the educator and judge, as well as those of the rope-dancer and bear-leader, which can be dispensed with.(327) Indeed, the dividing line between material and intellectual production cannot, by any means, be closely drawn.(328) Section LI. The Same Subject Continued. The greater number of recent writers(329) have, therefore, come to be of the opinion that every useful business which ministers to the whole people’s requirement of external goods possesses economic productiveness.(330) But it makes a great difference to science, whether a view is considered true because no one has suggested a doubt of its correctness, or because all doubts as to its truth have been triumphantly removed. Section LII. Idea Of Productiveness.