Hebrews 4:12

"For the Word of God is living and active and sharper than any two-edged sword, piercing as far as the division of soul and spirit, of both joints and marrow, and able to judge the thoughts and intentions of the heart."

As is His Word, so is He.  God's Word is living because He lives.  Just as surely as we know, love, and serve the living God, so we are assured that His Word lives, as well. 
Consistent with continual activity by the one true God, so His Word is likewise active.  Though sin in its many manifestations dulls our senses to discern His movements, nonetheless He is ever active in His sovereign interactions with His creation. 

There is nothing He does not see (Hebrews 4:13), nothing which would surprise Him, nothing which could "catch Him off guard," since He sees the end from the beginning with absolute awareness, (Jeremiah 23:23, 24).  Morever, the living God "sees not as man sees, for man looks at the outward appearance, but the LORD looks at the heart," (I Samuel 16:7).

It is this spiritual scrutiny, this revealing of our heart, that confirms the uniqueness of the Word of God.  Because the heart is more deceitful than all else (Jeremiah 17:9), no one truly knows his own heart.  It is a work of the Holy Spirit in the life of the believer to continually reveal his heart to him, primarily through the tool of His blessed book. 

As we present our heart to the Holy Spirit, exposing it to the standards, admonitions, examples, exhortations, and purities of His truth, our very thoughts and intentions undergo spiritual surgery.  His scalpel of Scripture cuts deeply into the diseases of sin and self, and lays open the illnesses which need removal by confession, repentance, and forsaking.  The more thorough our yearning for His knife, the greater the healing, restoration, joy, and usability.