Underlying the arguments I will try to put forward, there is a claim and a hypothesis. My claim: Neurath"s encyclopaedism deserves to be though out as an important and specific program inside neopositivism. We know that neopositivist program for unity of science was not homogeneous, that there are three slightly yet important perspectives needing to be though out in its specific difference: Carnap corresponding to the logical development, Morris to the more pragmatic tendency, and Neurath performing the encyclopaedic trend. My hypothesis: Neurath"s encyclopaedism is of great significance for the formulation of a contemporary conception of unity of science. A statement which assumes that nowadays encyclopaedia becomes more and more the very model of science and thus that our actuality is giving reason to Neurath.