Some of the young Muslims – especially those who read Islamic books or even academic material – only love debating, arguing and talking about Islamic topics and issues (especially in `aqidah and fiqh) but they do not act on what they know. Their knowledge is almost academic and non-practical. Imam al-Ghazali is advising that this is wholly inconsistent and a big failing. It is inconsistent because a person ought to practice what they know and teach it to others and it is a failing and weakness because their knowledge should make them act but it does not and this is the most unfortunate kind of knowledge.