One of the important uses of the computer is simulation and the simulation technology is so perfect that the computer can simulate the launch of a rocket, volcano eruption, nuclear explosion, etc., but it is impotent in simulating human emotion and intelligence. The computer simulation is fully digital, which pertains to the rational category, but human emotion and intelligence pertains to perceptual category. Perceptuality is the intrinsic property of highly developed lives. Human desire, emotion, will and intelligence represent human life typically. Emotion, for example, works only when it is true, so it can not be fabricated because the simulation of emotion is always false. Desire, emotion, will and intelligence can not exist when they leave their subject. If the computer can realize these representations, we can regard it as a life.
There are two ways of simulations, model and digital. Obviously, material models can not simulate the spirit of human brain. Although the process of digital simulation is fully unreal, it gives the results that can be almost the same as in the real conditions. Digital simulation can give the results only, not the real procedures. For example, when a computer simulates a crash of speedy cars, the computer screen displays the accident with crash sound from loud speakers vividly. This is a "cheating", since there is not any real crash with sound in the computer, and it gives the results of the procedure after all. The representation of human emotion and intelligence is just the procedure or process not the results, and this is the key reason why the computer can never simulate human brain with digital technology.
Simulation is programmed by man in order to actuate the representation of the objects. The computer simulation technology can show the facticity of things, but it can not show the reality of any human inner characteristics. This does not mean that the computer is not able to simulate some of human perceptual features, but that the simulation, to human sense, is false because it is programmed extrinsically, not from human inside. This kind of simulated human figures does have commercial values, they can be used in Disney or for simple service places, and in principle, it has no difference with the toys that are able to move, cry, laugh and speak.
Now many scientists and engineers are vainly attempting to apply digital technology of computation to simulate or actuate human emotion and intelligence. Time will relentlessly prove that they have gone on a wrong way.