Early in this work, we pointed out that engineering requires a great deal of decision making. It is, in fact, the foremost activity in design. How does one make the necessary decisions? The most important decision of all is probably that of deciding with which part of the device or system one should begin when making a design for a new product. As an example, consider an electric car for which specifications have been established as to the number of passengers, battery type, cruising speed, acceleration, and range. One can easily envision a number of subsystems of the vehicle, such as the drive motor system, suspension, drive train (if any), steering mechanism, and so forth. The designer must choose one of the subsystems as the one which will be designed first. Is there a logical way to make this choice?