Context of deliverance from error
Al-Ghazali contented that for knowledge to be certain, it must always remain free of doubts, illusion and possibilities of error. To him, “knowledge that is not infallible is not certain knowledge.” He evaluated the various branches of knowledge available during his time. From the analysis, al-Ghazali embraced the view that all knowledge are to be denied. His reasons are based on the following two issues: reliance on sense-perception, and reliance on intellectual truths. These two, representing the philosophy of empiricism and rationalism respectively, are the two major schools of thought in discussions on epistemology.
Since al-Ghazali had acclaimed that for knowledge to be certain, it has to be free from doubt, he launched a series of analysis to see whether he could make himself doubt either or both sense-perception and intellectual truths. The outcome extinguished whatever reliance he had on both.
To demonstrate the falsity of sense-perception, al-Ghazali used our sense of sight as an example. Al-Ghazali claimed that sight is the most powerful sense. But yet, when it looks at the shadow of a stick, it sees it standing still, and judges that the shadow has no movement. However, if one were to observe the situation after an hour, one would know that the shadow is moving. It moves gradually and steadily but infinitely in small distances in such a way that it is never in a state of rest. Therefore, what we had observed through our sense of sight is proven to be wrong, thus should not be relied upon.
In another demonstration, this time to falsify intellectual truths, al-Ghazali began asking some profound questions to himself pertaining to his previous reliance on intellectual truths. He finally came to the assumption that perhaps behind all intellectual comprehension, there is another judge who, if he manifests himself, will show the falsity of intellect in passing any judgments. Even if this meta-physical comprehension...