Imagine a basic information machine. A system that plays with data to advance knowledge — and through it power.
You may imagine this construct in many ways.
Now imagine that one (relatively) independent part of this system will be used for a specific and, for the sake of argument, private purpose.
Say the independent element must make the whole think that the sky is orange.
Supposing the system works (and this means being geared towards stability) the other parts of the system have to interact with this information and at least some of them must counter erroneous information. That is, there must be something to say that the sky is actually blue.
If our element is powerful enough, the overall effect of it’s action might surpass the balancing effect of the rest of the system.
Now sometimes the sky is orange. If this is sunset, our previous information error might actually be correct. In any complex system, the equilibrium state of the information will not be perfect (pure truth), but a good enough approximation.
So, back to our case, one can picture the effect of propaganda as an independent action over an information system. The system is society.
If propaganda is used to impose a content such as “product X is the best” it tends to trigger balancing mechanisms information-wise.
But we must remember that different kinds of information can be conveyed: “Product X exists” for example. In this way, the system is not being led to mistake, but still there are deep consequences.
The information mechanism involved in this second example is much more subtle and complex.