The aim of my PhD project was the clarification of the relationship between our commonsense experience and the scientific explanation of the world around us. The sciences claim to provide knowledge of a special quality. The indication ‘scientifically proven’ for instance refers to the outstanding reliability of the findings and the verification procedures of the sciences. If this claim is not to be taken as an empty promise, it has to be shown wherein this particular quality consists and in which way it differs from other forms of human knowledge, such as our ‘everyday’ knowledge. The determination of this relationship therefore presents an internal characterisation of the scientific knowledge, which constitutes one of the main tasks of the Philosophy of Science. To this end, the PhD thesis elaborates a distinctive criterion capable of differentiating between both forms of human knowledge. Given the fact that the relationship between the everyday experience and the scientific knowledge can be conceived in three different ways, the thesis discusses these different positions seriatim, in order to single out the most tenable position. In conclusion, the following view is put forward: Our everyday conceptions take their origin in the different practices and interests that are pursued within our life-world. They are to be judged according their ability to back our everyday practices. The adequacy of these concepts and distinctions does not reside in some correspondence to reality but in their appropriateness to the realisation of the different ends and practices that constitute our everyday business. The sciences have to be judged as well according their ability to back practices, namely the experimental and laboratory practices, which aim at a verification of the scientific theories. A scientific assertion has to be regarded as true and justified if, and only if, it leads to experimental success. The sciences are in addition subjected to the demand of a distinct and situation-invariant reproducibility of their results. For this purpose a standardisation of the scientific concepts is needed, which can rely on commonsense distinctions and concepts as its methodological starting point. As the particular quality of the sciences is located in this claim to distinctness and situation-invariance they cannot be regarded as per definition superior to our everyday knowledge. The alleged superiority of the sciences in the realisation of different ends rather has to be judged on a case by case basis and in direct comparison to the corresponding commonsense knowledge.