The delights of Knowledge are relative to previous Ignorance; for, although the possession of knowledge is in many ways a lasting good, yet the full intensity of the charm is felt only at the moment of passing from mystery to explanation, from blankness of impression to intellectual attainment. This form of the pleasure is sustained only by new acquisitions and new discoveries. Moreover, in the minor forms of the gratification due to knowledge, we never escape the law of relativity; the "power" delights us by relation to our previous impotence. Plato supposed that, in knowledge, we have an example of a _pure_ pleasure, meaning one that had no reference to foregone privation or pain; but such "purity" would be a barren fact, not unlike the pure air of a bladeless and waterless desert. A state of uninterrupted good health, although a prime condition of enjoyment, is of itself a state of neutrality or indifference. The man that has never been ill cannot sing the joys of health; the exultation of that strain is attainable only by the valetudinarian. * * * * * These examples have been remarked upon in every age. It is the moral weakness of being carried away by a present strong feeling, as if the state would last for ever, that blinds each of us in turn to the stern reality of the fact. There are, however, numerous instances, coming under Relativity, wherein the indispensable correlative is more or less dropped out of sight and disavowed. These are the proper errors or fallacies of Relativity, a branch of the comprehensive class termed "Fallacies of Confusion". The object of the present essay is to exhibit a few of these errors as they occur in questions of practical moment. * * * * * When it is said, as by Carlyle and others, "speech is silvern, silence is golden," there is implied a condition of things where speech has been in excess; and but for this excess, the assertion is untrue. One might as well talk of the delights of hunger, or of cold, or of solitary confinement, on the ground of there being times when food, warmth, or society may be in excess, and when the opposing states would be a joyful change.