So, if we say: “The greatest enemy of knowledge [or discovery] is not ignorance, it is the illusion of having knowledge” , it means that a failure to grasp the full extent or accurate knowledge of a matter can cause one to act in a way detrimental to achieving new discovery or wisdom. Any scientist, even a baker, and many a layperson knows that contaminated, insufficient, or inaccurate input, processes, understanding, etc. can lead to undesirable results. To say it differently, acting on inaccurate or incomplete knowledge prevents the desired outcome. Whether in science, secular pursuits, or spiritual matters, possessing only an “illusion of knowledge” can spell disappointment, if not ruin.
In the above statement given by Stephen Hawkings he is giving the importance of Knowledge. He wants to say that not knowing something is not a crime but claiming yourself of knowing everything despite knowing nothing leads you to darkness.
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