This paper aims to reveal parallels between the phenomenological concept of the life-world in Edmund Husserl and Maurice Merleau-Ponty and the naturalistic epistemology of Gerhard Vollmer, in which a central concept is the mesocosmos (“world of medium size”). Such a comparison is necessary because the concepts of life-world and mesocosmos are quite similar in content, since they both refer to the human dimension of our world experience, to our natural position in the world. However, these concepts are far from identical. In Husserl’s case, the world of life is the world of pre-scientific experience taking place before scientific idealizations. According to Merleau-Ponty, the world of life is primarily a world of perceptual experience, in which I participate not as a subject of culture, but as an anonymous subject of perception, as a living perceptive body. Both philosophers call for a return to the life-world as a ground of scientific idealizations in order to overcome a crisis brought about by an excessive trust in scientific knowledge and “objectifying thinking”. In turn, Vollmer interprets the mesocosmos as a “world of medium size” that we can successfully explore due to the evolutionary adaptation of our cognitive abilities. This is our “ecological niche”, but while Husserl and Merleau-Ponty encourage us to return to this “cradle of humankind” to take root in it, Vollmer emphasizes that we are not bound to our ecological niche and can expand our knowledge both in the direction of the microworld and in the direction of the “world of mega scales”. He calls this process the objectification and deanthropomorphization of our picture of the world, and this is, in his view, the main trend of the development of scientific knowledge in its history, which is supported by the views of some prominent scientists of the 20th century.