How can a person be physically alive but spiritually dead? Are we talking the walking dead or some kind of zombies?
The Bible teaches that human beings, created by God, are both physical and spiritual beings.
Mankind was not originally created to die, neither spiritually or physcially. Both types of death are the consequence of Adam's sin:
"...sin entered the world through one man, and death through sin, and in this way death came to all people, because all sinned" (Romans 5:12).
Death was the punishment for sin (Romans 6:23).
Physical death separates us from those we love. Likewise, spiritual death separated mankind from God. That's how we start life. But God already had a solution in mind. Jesus said,
“Very truly I tell you, whoever hears my word and believes him who sent me has eternal life and will not be judged but has crossed over from death to life" (John 5:24).
When you put your faith in Christ as Savior you "crossed over" from death to life spiritually!
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Fact: A spiritually dead (separated from God) person can still be aware God exists. Not only is there a witness to God in Creation (Romans 1:20), but God's Holy Spirit has the ministry of "convicting" the world of the reality of sin, the righteousness of Christ, and that fact that there is a judgment to come (John 16:8-10).
And we are made in God's image, though fallen. It's like the ruins of a once great building. You know there is a building--you just may not be able to see what it once was like.
But this awareness alone is not enough to cross over from death to life. We must put our trust in Christ as our Savior (John 1:12; 3:16; 5:24).
All of us are born physcially "in Adam," and spiritually dead, separated from God.
"For as in Adam all die, so in Christ all will be made alive" (1 Corinthians 15:22).
If we leave this physical life still spiritually dead and separated from God then it becomes eternal separation from Him (Revelation 20:14). We need to be "in Christ." How? We need a second birth (John 3:3), to be born again spiritually through faith in Christ.
Peter told believers,
"For you have been born again, but not to a life that will quickly end. Your new life will last forever because it comes from the eternal, living word of God" (1 Peter 1:23).
Good news! The instant you put your faith in Christ you received eternal life that will never end. Now pass that good news along!