**3. Mechanical requirements and engineering challenges**

It is a matter of philosophical discussion how far it is possible to discuss hardware and software separately. Section 4.2 in particular will discuss theories from cognitive science which indicate that in the human, body and mind are intrinsically intertwined and that some of the hardware can in fact be considered to fulfill certain roles of the software too. However, entering into such a debate in detail is beyond the scope of this chapter. Therefore, when considering the different components of Rob's robot, we will largely separate hardware and software in the sense that we will discuss purely mechanical requirements first and computational requirements next. Since hardware can fulfill computational requirements and mechanical requirements can impose software requirements as well, there may be some natural overlap, which in a sense already illustrates the validity of some of the ideas from embodied cognition (to be discussed in section 4.2.1).

First then, Rob needs to identify mechanical and engineering requirements for the creation of his humanoid robot. He is interested in particular in the state of the art of components like sensors and actuators, and must consider how close these elements are to his ambitious requirements and what major challenges still need to be addressed before his vision can become reality. The remainder of this section is dedicated to answering these questions.
