  Together with the mutation of ideas, new forms recognized in sensations occur. First, when observing phenomena of a new kind one reaches for the set of known forms—and starts to recognize that this, what is new, sometimes and under a certain respect resembles what is known, but some other times and under other respects it is different. In this period descriptions of results of experiments are full of comparisons with what one earlier learned to perceive, but also are full of provisions that those comparisons are sometimes unreliable. The unreliability manifests itself in the unrepeatability of initial experiments: something goes differently than before, and we know neither why it was so, nor what to do in order to get the same result next time. This raises concerns and the readiness for change. A researcher acting more or less blindly, searches for some constraints of thought: