The emergence of mind from body is one of the topical subjects of the modern Philosophy of Mind. The present paper analyses how this problem – according to Mach and Uexküll – can be connected with a naturalization of knowledge. Both scientists pointed out that knowledge and science result from a long natural development: they would originate from body and sensibility; in this case scientific instruments are nothing else but a supplementary sensory, that modifies the body itself and its sensibility. According to this, scientific instrumentation and knowledge itself have a very restricted power: suggested from the 19th German physiologist Johannes Müller (and strongly influenced from the debate about a priori conditions of knowledge in the late 19th German Philosophy), Uexküll points out that the function of the organisme, through its organ senses, is to select an adapted nature; the senses represent the way to create this form of adaptation. Indeed the Müllerian principle of specifical sense energies (for instance: the eye feels any stimulus as light sensation) showed the sensibility have an active rule in the process of representation and in knowledge. That means, organisms with a different sensory-organization feel a different world. Then – according to Mach – knowledge and science are an adaptive answer to human needs: as well as each sense organ, scientific instruments – theoretical and material knowledge instrumentation – can feel all, but in a ‘specifical manner’, depending on their structure. They represent and depict a sight, a perspective (Seite), not an exhaustive part (Teil) of the world. The world itself is given as an infinite variety of perspectives, each one deeprooted in its sensory, in its ‘body’, in its nature – each one as a quite different adaptive answer to its Umwelt and as a form of it.