Conventional: Being without a means of protecting yourself from attack, and so being completely vulnerable to harm.
ACIM: The attitude and response that stems from realizing that you cannot be attacked or harmed, that you are invulnerable. It thus comes from strength and leads to safety. Ironically, defensiveness is what lays you open to attack by affirming that attack is real and you are vulnerable. See defense and invulnerability. See W-pI.153, M-4.VI.