The problem is with your definition of 'dead.' It does not mean unconscious/unable to respond. It means separation. Physical death is separation from the body. We see the body lying there and think of death as unable to respond, but the soul, which inhabited the body is simply gone and still very much in existence.
In John 17:3, Jesus stated that eternal life is knowing the Father and the Son. Therefore eternal death is NOT knowing the Father and the Son. The 'knowing' here is the intimate knowing of a close relationship, not intellectual acknowledgement. In other words, spiritual death is separation from God.
If it were truly a sort of spiritual unconsciousness/inability to respond, then the Bible has some serious problems. First of all, hell would have no meaning whatsoever in terms of human beings. Second, God's invitation to 'Come let us reason together' in Isaiah 1 is hogwash, for there would be no way a spiritually dead person could reason. Third, Jesus' invitation to "Come unto me all ye that labor and are heavy-laden" would not mean that at all, but rather be a summons only to the elect. Fourth, John 3:16-18 would be nonsense, for it would not be a matter of belief or unbelief (how can a spiritually unconscious/unresponsive person respond with unbelief?), but a matter of simple uncontrollable election.
Spiritual death does not mean one cannot respond to spiritual matters. The entire Bible is predicated upon the opposite -- the the spiritually dead man CAN respond to God or at least to the truth he or she is initally presented with, and at least WANT what is true and good, even if that is unattainable in the unredeemed state. God judges the heart... He knows who wants Him and He will lead those who do want the truth and the good to Christ, who then refuses none whom the Father leads to Him.