That's why it's important to grab the meaning of a word when it comes to the Bible. By meaning I mean interpretation, not necessarily translation. The word knowledge, for instance, is used to cover so many other words: wisdom, understanding, intimacy with God, the fear of God, and many, many, many more. (Check Pro. 2:1-6 and then on to the end of the chapter.) I say this all to say that when it talks about a lack of knowledge in the passage you mentioned, it's talking about a lack of revelation or understanding, not what we think of as knowledge.
There are many other passages where all these words are used interchangeably, but they all have their own distinct meanings. People don't perish just because they don't 'know' but often because they have received no revelation (which is a knowledge that is within you in such a way as to motivate and influence your life). God's people perish for lack of revelation, not lack of 'knowledge'. If you look at Pro. 29:18 in different translations, you will see that "Where there is no vision" basically means "where there is no revelation (inner illumination)". Revelation and wisdom are twins: the former gives you light (knowledge); the latter tells you what to do with it. Because of the primary importance of wisdom (first) and revelation (alongside it), Paul said in Eph. 1 that he prayed for God to give the Ephesians "a spirit of wisdom and revelation in the knowledge of Him."
Because a Christian cannot ever know and grasp or understand God and His ways without "a spirit of wisdom and revelation" (Jesus told His followers this same thing several times), which is simply a manifestation of the Holy Spirit as merged with the human spirit (look at 1Jn. 2:20, 26-27 where this merge is called "the anointing that remains within you" rather than the Holy Spirit or the human spirit), there are many Christians who have lots of information but who don't know who God is. The s is small in the Eph. 1 passage because it isn't just the Holy Spirit nor can it be an evil spirit nor the human spirit alone which has no ability to understand God alone; same in 1Jn. 2 with 'the anointing'. Without this 'spirit' which mentors us in the knowledge of God and this 'anointing' which teaches us the things of God (same thing), no person, Christian or non, is able to grasp, understand, or really come to know God and the ways and things of God. Wisdom is the foundation of everything that God builds (and without it, Christians are a complete wreck) as it says in Proverbs, and it is always at the beginning of God's works as Proverbs also says.
