This could lead to many mistakes in philosophy. In politics deception may come from anyone with any motivation that doesn’t lead to the greater good. And even those which have the greater good firmly in mind may at times be deceived or manipulated by those who do not.
In epistemology, an ignorance of deception may lead the philosopher to erroneously assume that everyone has the motivation to find the truth just as they do.
The motive to deceive philosophers is very high, since traditionally they have exposed many errors that have stripped many people of their power. Also, philosophers have sometimes been very influential—a very enviable position.