The following considerations concern the structure of the "life world" as conceived by Husserl, in which we, as humans, experience nature, culture, and society in a natural attitude, take positions regarding these, are influenced by them, and act upon them. In this attitude, the existence of the life world and the typical character of its contents are taken as given without question. As Husserl showed, our thinking occurs under the ideal of "and so on" and "I can always again": the former leads to the assumption that what has been valid in our experience so far will remain valid; the latter leads to the expectation that I can, what I have already achieved in this world and through it, achieve again and again in the future. We can therefore speak of fundamental assumptions that are characteristic of the natural attitude in the life world and are taken as given without question: namely, assumptions of the constancy of world structure, the constancy of the validity of our experience of the world, and the constancy of our ability to act upon the world and within it. What is taken as given is, in the first approximation, the "self-evident," which, as such, forms a form of our world and self-understanding in the natural attitude. However, it belongs to the nature of what is taken as given without question that it can at any time be questioned, and even the self-evident can at any time become unintelligible. Indeed, the assumptions of constancy themselves are only valid until proven otherwise: expectations based on the constancy of world structure may "explode," making the valid doubtful and the possible impossible. What was previously taken as given becomes a problem, a theoretical, practical, or emotional problem that must be formulated, analyzed, and solved. However, all problematical issues arise from the original given (which, in the true sense, becomes "questionable"), and all problem solutions consist in transforming the questionable into something new that is given again through the process of questioning. Even the unexamined self-evident has open inner and outer horizons that are given to us in the natural attitude for possible interpretation. To solve the emerging practical and theoretical problem that arises from the questioning of what was previously self-evident, we must enter into these horizons. However, we abandon this endless task as soon as we believe we have sufficient knowledge of what has become questionable, and then declare the problem as solved for our purposes in a seemingly arbitrary decision. But how does a problem arise, that is, why does what has become questionable seem worthy of questioning? What is relevant for solving a problem? When does it seem to us that it is sufficiently solved for our purposes so that we can stop further investigation? All these questions aim at different meanings of the concept of "relevance," which we will analyze further below. First, we must confirm in a condensed form some basic structures of the life world assumed asThe following considerations concern the structure of the "life world" as conceived by Husserl, in which we, as humans, experience nature, culture, and society in a natural attitude, take positions regarding these, are influenced by them, and act upon them. In this attitude, the existence of the life world and the typical character of its contents are taken as given without question. As Husserl showed, our thinking occurs under the ideal of "and so on" and "I can always again": the former leads to the assumption that what has been valid in our experience so far will remain valid; the latter leads to the expectation that I can, what I have already achieved in this world and through it, achieve again and again in the future. We can therefore speak of fundamental assumptions that are characteristic of the natural attitude in the life world and are taken as given without question: namely, assumptions of the constancy of world structure, the constancy of the validity of our experience of the world, and the constancy of our ability to act upon the world and within it. What is taken as given is, in the first approximation, the "self-evident," which, as such, forms a form of our world and self-understanding in the natural attitude. However, it belongs to the nature of what is taken as given without question that it can at any time be questioned, and even the self-evident can at any time become unintelligible. Indeed, the assumptions of constancy themselves are only valid until proven otherwise: expectations based on the constancy of world structure may "explode," making the valid doubtful and the possible impossible. What was previously taken as given becomes a problem, a theoretical, practical, or emotional problem that must be formulated, analyzed, and solved. However, all problematical issues arise from the original given (which, in the true sense, becomes "questionable"), and all problem solutions consist in transforming the questionable into something new that is given again through the process of questioning. Even the unexamined self-evident has open inner and outer horizons that are given to us in the natural attitude for possible interpretation. To solve the emerging practical and theoretical problem that arises from the questioning of what was previously self-evident, we must enter into these horizons. However, we abandon this endless task as soon as we believe we have sufficient knowledge of what has become questionable, and then declare the problem as solved for our purposes in a seemingly arbitrary decision. But how does a problem arise, that is, why does what has become questionable seem worthy of questioning? What is relevant for solving a problem? When does it seem to us that it is sufficiently solved for our purposes so that we can stop further investigation? All these questions aim at different meanings of the concept of "relevance," which we will analyze further below. First, we must confirm in a condensed form some basic structures of the life world assumed as