What does Hebrews 5:14 mean?
When a child is very young, they can only consume milk. Foods with more substance are beyond them; they can only process something specifically meant for infants. In the same way, those who are spiritually immature can only deal in simpler spiritual matters. This is not bad, when a person is a new convert. However, if a person remains in this state of spiritual infancy, when they should have grown enough to handle more solid spiritual "food," then they have only themselves to blame (Ephesians 4:11–15). According to the writer of Hebrews, his target audience is going to miss some of the deeper meanings he will describe (Hebrews 5:11), since they are "dull of hearing." In this context, that "dullness" means laziness and apathy.Just as a child has to be trained to grow beyond milk to eating solid food, so too must a Christian's spiritual maturity grow through effort and experience. The prior verse used the term apeiros to describe these spiritual babies, meaning they are inexperienced or unskilled. Spiritual maturity has nothing to do with age, since it's possible to remain an immature Christian for a long, long time. Rather, maturity involves developing the ability to put our faith to practical use.
In the context of the book of Hebrews, this has everything to do with making a purposeful effort. It requires that a person "pay much closer attention" to the faith (Hebrews 2:1). It means Christians are to follow God's will without fear and without disobedience (Hebrews 4:11). Maturity requires that a person learn to use our greatest spiritual tool, the Word of God (Hebrews 4:12), in order to aid our discernment. The end result, according to this verse, is a person who can distinguish between good and evil. This is about more than just moral dilemmas—it's also a reference to knowing the difference between truthful, godly teaching and worldly, false faith.