The questions which we will consider here are "What is AI?" and "How can we make AI?". Here we will present the definition of AI in terms of multi-agent systems. This means that here you will not find a new answer to the question "What is AI?", but an old answer in a new form. This new form of the definition of AI is of interest for the theory of multi-agent systems because it gives us better understanding of this theory. More important is that this work will help us answer the second question. We want to make a program which is capable of constructing a model of its environment. Every multi-agent model is equivalent to a single-agent model but multi-agent models are more natural and accordingly more easily discoverable.