A logo is many things to many people, but I believe it is in fact a simple thing. A logo is a vessel, a symbol. Even the most beautifully looking one doesn’t necessarily have to be a good logo. This is because a logo is not just about how it looks, but mainly about what it contains in terms of meaning.
To have a strong logo you need to fill that vessel with powerful brand meaning, which is created slowly and on many levels. Then at the end the logo becomes simply a reference point to all that meaning and all those experiences related to the brand. It is similar to the address of a house or the name of a person. They are all symbols, and their strength comes with time, when you start to know them more, to create memories with them.