If we are in a text editor, for instance, and we press a key corresponding to a letter, that letter will show on the screen. For the unaware, it is difficult to imagine that by pressing a key associated with a letter, a register-accumulator will make hundreds or thousands of logical and arithmetical operations on binary numbers, only to have that letter shown on the screen. This example wants to illustrate that, based on the external analysis of what is happening, it is impossible to figure out the principle of work of a ridiculously simple device as a computer (ridiculously simple compared to the brain of a dog, e.g.) The method used in positive sciences is not the analysis of primary data. The method of analysis works on extremely simple systems, which can be perceived on image models as well. The method used in positive sciences is to guess a symbolic model, based more or less on the interaction with external reality, and to verify the model. It results that the method of understanding the brain based on the analysis of primary data is at least inefficient. A fundamental problem of knowledge is that primary facts can be understood only if a model to integrate them already exists. Without a model, we are forced to build one on the spot. Thus, each fact of the external reality could be understood based on a local model. The correlation between facts, each understood in its local model is impossible. This is why a method of guessing a fundamental model was imposed. Based on the single fundamental model the facts are interpreted and reinterpreted. Such a method allows the correlation of the primary facts. If the model does not make good predictions, it will be modified and the process restarted from scratch, until we find the model in which all the primary facts can be understood. The process stops when the predictions are true with an acceptable rate. In that phase we can talk about knowledge. As a comment, we need to say that the analytical method is based on short- range models (can be affected by schizophrenia and XSPC), while the synthetic method is based on long-range models which allow not only correlation between facts, but also a cross-check between the local models. The need for a single fundamental model comes from the fact that any used word needs to have a unique definition. This is true only in case of the existence of a single fundamental model. Example: what would happen if in common language everybody used different definitions for the words used? The communication would not exist, everyone talking his/her own language. The conclusion is that any positive science is based on a single fundamental model, stated from the very start. This symbolic model can be based on primary facts, results of the interaction with external reality or on theoretical principles (e.g. the principle of inertia in Newton's Mechanics cannot be visibly connected by facts seen in the external reality).