Listen to the following statements of Alexander von Humboldt, which he makes in the initial argument of his "Cosmos" in regard to speculation: "The most important result of physical research by sense perception is this: that it finds the element of unity in a multitude of forms; that it grasps all the individual manifestations offered by the discoveries of recent times, carefully scrutinizes and distinguishes them; yet does not succumb under their mass; that it fulfills the sublime mission of the human being, of understanding the nature of things which is hidden under the cover of phenomena. In this way our aim reaches beyond the narrow limits of the senses, and we may succeed in grasping the nature by controlling the raw material of empirical observation through ideas. In my observations of the scientific treatment of general cosmic phenomena, I am not deriving unity out of a few fundamental principles found by speculative reason. My work is the expression of a thoughtful observation of empirical phenomena seen as one and the same nature. I am not going to venture into a field which is foreign to me. What I call physical cosmology does not, therefore, aspire to the rank of a rational science of nature.... True to the character of my former occupation and writings, which were devoted to experiments, measurements, and investigations of facts, I confine myself in this work to empirical observations. It is the only ground on which I can move with a measure of security." In the same breath Humboldt says that "without the earnest desire for the knowledge of concrete facts any great and universal world philosophy would be merely a castle in the air" and in another place that "an understanding of the universe by speculative and introspective reason would represent a still more sublime aim" than understanding by empirical thought. And on page 68 of volume I. he says: "I am far from finding fault with endeavors of others the success of which still remains in doubt, when I have had no practical experience with them."