This paper critically examines J.J. Thomson’s arguments in “A Defense of Abortion” (1971), focusing on her defense of bodily autonomy against anti-abortion claims. It argues that while Thomson successfully demonstrates through her famous Violinist Analogy—that a fetus’s right to life does not automatically override a woman’s right to control her own body, her position remains incomplete when addressing the moral implications of consent and fetal agency. Using deductive analogies, the paper first reconstructs Thomson’s reasoning to show how her arguments challenge the assumption that abortion is always morally impermissible. It then introduces the hypothetical case of the “self-aborting fetus,” a thought experiment that reverses the dependence relation between mother and fetus, to test the limits of Thomson’s framework. The analysis suggests that, although Thomson’s defense of abortion compellingly upholds the principle of bodily autonomy, it leaves unresolved questions concerning mutual rights and moral responsibility in cases of shared vulnerability.