I began to question many things when I discovered that for over a thousand years before the Protestant Reformation, the Roman Catholic Papacy had dragged every stripe and type of pagan philosophy into Christianity and baptized it as "Biblical" or "tradition worthy". Chief among these errors is the first lie in Scripture told by the devil: "Thou shalt not SURELY die." Today, you and many other Christians accept this lie. Oh, you'll admit the one lying in the casket is dead....BUT NOT SURELY. They're alive somewhere, in heaven, hell, Purgatory...
The reason is because BAPTIZED PAGANISM has taught you that that a "soul" is not what the Bible says - that which exists ONLY as a consequence of the union of the Body and the Breath of Life (Genesis 2:7 KJV). IOW, man does not POSSESS a soul - man IS a soul; the combination of the Body and God's Breath of Life.
The lie you choose to believe is that man is NOT a "soul", but has a "soul" residing in him, which at his death flies off as an immortal, transparent poltergeist which looks, thinks, feels, and knows all as the dead person did.
Of course, the Bible plainly teaches nothing of the kind, as the OP title proves. "The soul that sinneth, it SHALL die."