We learn words in certain circumstances. Then, obviuosly, we expect that we can use them in similar circumstances in a similar way. Others learn words in certain circumstances too and then they expect that it is possible to project them into similar circumstances in a proper way. But nothing can assure us that these expectations will actually be fulfilled. For there is no "book of rules" that makes sure that we understand projections of others and similarly that others will understand what we have absorbed so far. So how is it possible that we understand one another? – Wittgenstein suggests that our ordinary communi-cation (as well as, for example, our understanding of behaviour of others) rests upon the basis which he metaphorically calls "our common form of life". There is no foundation that can properly explain our mutual understanding other than these common opinions, interests and aims gained in the experience of life.