General argument for Islam.

[Mystic]

Also, what is 'knowledge which is contrary to actions performed with sincerity'? Example?

It is when you know God, his Oneness, his Divine Names, the descent of his Name and the ascension towards him, are aware of the trial, aware of the reward of good, aware of God's rights and the morals, and aware of spiritual realities of the 7 heavens, 7 earth, the veils of light, the position of the Prophets, the connection companionship of the Imams that Guide by God's command, yet as the Quran states "but he (despite being given of God's Signs/guidance) sticks to the earth".

This knowledge is useless and would be a proof against you. It's the type where someone has it intellectually in his mind, understands, but his heart really disbelieves in it and doesn't have faith in it. This type of knowledge is actually not true knowledge, but a delusional type. It's affirmation with the mind, words, lip service, but the soul isn't convinced and has not verified it with sincerity.

This is not my explanation, but this is what the Imam meant, if you read the rest:

 

Knowledge is the basis of every sublime state and the culmination of every high station. That is why the Holy Prophet said, 'It is the duty of every Muslim, man and woman, to seek the knowledge,' that is, the knowledge of precaution (taqwa) and certainty. Imam 'Ali (‘a) said, “Seek the knowledge, though it be in China,” meaning the knowledge of gnosis of the self, in it is contained knowledge of the Lord.
 
The Holy Prophet said, 'Whoever knows his own self knows his Lord; moreover, you should acquire that knowledge without which no action is correct, and that is sincerity ... We seek refuge with Allah from knowledge which has no benefit', that is, from knowledge which is contrary to actions performed with sincerity.
 
Know that a small amount of the knowledge requires a great deal of action, because the knowledge of the Hour requires the person who has such knowledge to act accordingly during his entire life. ‘Isa (‘a) said, 'I saw a stone on which was written, "Turn me over", so I turned it over. Written on the other side was "Whoever does not act by what he knows will be doomed by seeking what he does not know, and his own knowledge will be turned against him." '
 
Allah revealed to David, 'The least that I shall do to someone with knowledge who does not act by his knowledge is worse than the seventy inner punishments which result in My removing from his heart the sweetness of My remembrance.' There is no way to Allah except via knowledge. And knowledge is the adornment of man in this world and the next, his driver to Paradise, and by means of it he attains Allah's contentment with him.
 
He who truly knows is the one in whom sound actions, pure supplications, truthfulness and precaution speak out; not his tongue, his debates, his comparisons, assertions or claims. In times other than these, those who sought knowledge were those who had intellect, piety, wisdom, modesty and caution; but nowadays we see that those who seek it do not have any of these qualities. The man of knowledge needs intellect, kindness, compassion, good counsel, forbearance, patience, contentment and generosity; while anyone wishing to learn needs a desire for knowledge, will, devotion (of his time and energy), piety, caution, memory and resolution