13
culminating in birth, the spouses discover not only the mystery of creation, but also re-discover
themselves in light of God’s original plan for marriage. It is here that St. John Paul II specifically
enfolds the mystery of human fertility within the nuptial embrace, which “stops being something
passive. It reaches the specific level and content of self-conscious and self-determinant
persons.” 40 Therefore, fertility—inextricably bound up as it is with sexuality—has a fundamental
role in confirming and renewing the image of God in each of the spouses.
However, it is not enough for the couple to simply read the biological signs inherent in
the fertility cycle; rather the spouses must respond to these signs in keeping with God’s design,
using a well-formed conscience as interpreter. 41 Humanae Vitae warns that “to use this divine
gift while depriving it, even if only partially, of its meaning and purpose, is equally repugnant to
the nature of man and woman and is consequently in opposition to the plan of God and His holy
will.” 42 A proper awareness and understanding of this two-fold gift of fertility and sexuality is
paramount in order to make rational and free decisions regarding its use. To this end, the signs of
fertility in a woman’s body throughout her cycle not only present for discernment the “biological
laws that apply to the human person,” 43 but also provide a lens through which God reveals the
mystery of creation, and consequently, the mystery of God’s inner life to the couple. As a
reflection of the communion of love and life of the Trinity, husband and wife must read the signs
of their fertility as a “unity of the two,” 44 responding to this language of the body—as Humanae
40
Ibid, para. 8.
HV, sec. 10.
42
Ibid., sec. 13.
43
Ibid., sec. 10.
44
John Paul II, Mulieris Dignitatem [On the Dignity and Vocation of Women], Vatican.va, August 15,
1988, sec. 11, accessed May 27, 2018, https://w2.vatican.va/content/john-paul-
ii/en/apost_letters/1988/documents/hf_jp-ii_apl_15081988_mulieris-dignitatem.html.
41