The knowledge is relevant , reliable , and valid . Reliable implies that the information is consistently true and can be depended upon. It has been tested repeatedly by practitioners and found to apply consistently over time. So if your information is reliable and valid, it is true, trustworthy, and will produce the effects you desire. Relevance implies that the information applies specifically to the issue at hand.
Relevant information means that one has accessed an appropriate frame for the problem at hand.
Relevance is important because information is specific to its frame of reference. On the surface it may appear that information freely crosses the borders of disciplines. It does not. That is to say, an expert in one discipline may be a misinformed amateur in another. Time in one discipline is measured in millions of years and in another in nano-seconds.