This book aroused a lively controversy, the writer's theories and conclusions being attacked and defended by various writers. The great interest excited by his essay caused Malthus to enquire still more deeply into the phenomena of poverty, and he determined to travel through Europe for the purpose of collecting facts bearing upon the subject. In 1799 he visited the continent, passing through Denmark, Sweden, and part of Russia, and, later, Switzerland and Savoy. The results of his researches furnished overwhelming proof of the accuracy of his contention; and in 1803 he published a second and much enlarged edition of his Essay, in two volumes. During the remainder of his life, Malthus thrice edited new editions of his work, which to this day remains the greatest monument of his honorable career. He died on 29th December, 1834. It is not intended here to give an exhaustive analysis of Malthus's Principle of Population. [1] We are concerned only with his theory of population and the conclusions to which that theory points. "The principal object of this essay," says the author, "is to examine the effects of one great cause intimately connected with the very nature of man, which, though it has been constantly and powerfully operating since the commencement of society, has been little noticed by the writers who have treated this subject. The cause to which I allude is the constant tendency in all animated life to increase beyond the nourishment prepared for it. "Dr. Franklin has observed that there is no bound to the prolific nature of plants or animals but what is made by their crowding and interfering with each other's means of subsistence. Were the face of the earth, he says, vacant of other plants, it might be gradually sowed and overspread with one kind only--as, for instance, with fennel; and were it empty of other inhabitants, it might in a few ages be replenished from one nation only, as, for instance, with Englishmen. "This is incontrovertibly true. Through the animal and vegetable kingdoms Nature has scattered the seeds of life abroad with the most profuse and liberal hand; but has been comparatively sparing in the room and the nourishment necessary to rear them. The germs of existence contained in this earth, if they could freely develop themselves, would fill millions of worlds in the course of a few thousand years. Necessity, that imperious, all-pervading law of Nature, restrains them within the prescribed bounds. The race of plants and the race of animals shrink under this great restrictive law, and man cannot by any efforts of reason escape from it.