Another reason not to base a doctrine on the meaning of a word is that languages change over time, and modern Greek and Hebrew can differ significantly from biblical Greek and Hebrew. The exact meaning of a word in ancient times is not always certain, and therefore, more is required than looking up a word in a concordance or other study aid. Lexicons and Biblical dictionaries can help, but they are just that - a help, not a solid base. They have their place, certainly, but their definitions must be tested against biblical usage.
If you have been in the church for any length of time, you've probably observed that resting a teaching on the meaning of a word leads to arguments about words, which Paul warns against (I Timothy 6:4). Instead of meaningful discussions about the whole counsel of God, this approach encourages heaping up teachers (II Timothy 4:3) - such as scholars or reference works - that agree with a specific definition. Yet this is dangerous, because you can find support among scholars for almost any perspective, even ones that are anti-God.
