The Orthodox Church teaches that the Theotokos was sinless in the sense of having never personally sinned. She was sinless by grace, needing the Savior, whereas Christ was sinless by nature, being the Savior.
How can this be?
The notion of the Fall means that we are born needing the Savior, and not as a consequence of anything we have personally done. We sin because we are Fallen; we are not Fallen because we sin. Our condition of being Fallen precedes our personal acts of sin. Thus, even though we may have never personally sinned, we are still constitutionally Fallen, which is to say the principle of sin and death is still operational within us even if we have not sinned personally.
Scripturally, this can be explained by what happened to the prophet Jeremiah: "Before I formed you in the womb I knew you, and before you were born I consecrated you (from qadash, meaning sanctified, hallowed, made holy); I appointed you a prophet to the nations" (Jeremiah 1:5).
In other words, if Jeremiah can be sanctified by God from the womb, then it is not impossible for the Theotokos to likewise be sanctified from the womb. This is not quite the same as the Roman Catholic doctrine of the Immaculate Conception, which the Orthodox Church does not affirm, but is instead the Biblical doctrine that one can be sanctified from the womb, prior to any personal act of sin, being made holy by a special act of the Lord on some person's behalf, preserved from acts of sin by grace and so set apart for some unique or special work on His behalf.
This does not mean that Jeremiah was sinless by nature, but by grace, and so he still required the Savior because his constitutional position, so to speak, was that of being one among the Fallen, despite being sanctified from the womb. Likewise, the Theotokos was one among the Fallen, though without ever having personally sinned in any way, set apart and sanctified in a way surpassing even that of the prophet Jeremiah, for she bore in her person the very Word of God.
In other words, if Jeremiah can be sanctified by God from the womb, then it is not impossible for the Theotokos to likewise be sanctified from the womb. This is not quite the same as the Roman Catholic doctrine of the Immaculate Conception, which the Orthodox Church does not affirm, but is instead the Biblical doctrine that one can be sanctified from the womb, prior to any personal act of sin, being made holy by a special act of the Lord on some person's behalf, preserved from acts of sin by grace and so set apart for some unique or special work on His behalf.
This does not mean that Jeremiah was sinless by nature, but by grace, and so he still required the Savior because his constitutional position, so to speak, was that of being one among the Fallen, despite being sanctified from the womb. Likewise, the Theotokos was one among the Fallen, though without ever having personally sinned in any way, set apart and sanctified in a way surpassing even that of the prophet Jeremiah, for she bore in her person the very Word of God.
