Were this science, there would be no dispute. We should have to admit that there could be no limit set to the freedom of this being; he must share the privileges of divine Intelligence, for no command to keep silent can be imposed on Infallible Truth; there can be no amendment. But, alas! in the world of reality this personified Science is nowhere to be found, it exists solely in the realm of rhetoric and poetry. Science, as it exists among men, has its seat, after all, nowhere else than in the human mind. It is, indeed, nothing else but _the well-ordered summary of knowledge and of the research for the causes of things_. Natural science is the summary of knowledge and research in the realm of natural phenomena, arranged in an orderly way, as a text-book will give it; that is, an investigation of phenomena and their causes. A mere description of natural phenomena, without any explanation, or reference of them to the laws of nature, would indeed be teaching about nature, but not natural science. Similarly, the science of history is the well-ordered summary of knowledge and research in the domain of human events, derived from their sources, with the statement of facts according to cause and effect. And not all this knowledge is certain, and free from doubt. The modern conception of science, as we now have it—the ancients had a much narrower conception—includes certain as well as uncertain knowledge, results and hypotheses, and even the activity of research, together with its methods. Astronomy was thus in _Ptolemy’s_ time the summary of what was then known with more or less certainty about the stars; included in this, as is well known, was the opinion that the sun circles around the earth. And the philosophy of _Aristotle_ embraced his philosophical ideas about God, the world and man; hence many errors. Further, when speaking of science in general, we mean the whole number of the individual sciences. It is the freedom of science in this sense that we have to investigate here. The individual sciences are distinguished one from another principally by the subjects of which they treat. Astronomy is distinguished from palæontology and philosophy by the fact that it treats of the stars, not of fossils, or of the fundamental truths of reason. From this brief analysis of concepts it is clear that science and scientific research are not superhuman beings, but an activity or condition of the human mind, distinguished from the ordinary thought of the individual only by system and method, and, commonly, by greater thoroughness and by the united effort of many. _It is subject to all the limitations of the human mind._ What follows from this? Two things. Let us at once make a brief reference to both of them, because in our discussion they are of the greatest importance.