Humanae Vitae is an encyclical letter issued on July 25, 1986 by Pope Paul VI. Humanae Vitae means "Of Human Life." In Humanae Vitae, Pope Paul VI appealed to various people, including men of science; and doctors and medical personnel.
Men of Science
"We wish now to express our encouragement to men of science, who can considerably advance the welfare of marriage and the family, along with peace of conscience, if by pooling their efforts they labor to explain more thoroughly the various conditions favoring a proper regulation of births. It is particularly desirable that, according to the wish already expressed by Pope Pius XII, medical science succeed in providing a sufficiently secure basis for a regulation of birth, founded on the observance of natural rhythms. In this way, scientists and especially Catholic scientists will contribute to demonstrate in actual fact that, as the Church teaches, "a true contradiction cannot exist between the divine laws pertaining to the transmission of life and those pertaining to the fostering of authentic congugal love." (Humanae Vitae, para. 24)
Doctors and Medical Personnel
"We hold those physicians and medical personnel in the hightest esteem who, in the exercise of their profession, value above every human interest the superior demands of their Christian vocation. Let them persevere, therefore, in promoting on every occasion the discovery of solutions inspired by faith and right reason, let them strive to arouse this conviction and this respect in their associates. Let them also consider as their proper professional duty the task of acquiring all the knowledge needed in this delicate sector, so as to be able to give to those married persons who consult them wise counsel and healthy direction, such as they have a right to expect." (Humanae Vitae, para. 27)
In Humanae Vitae, Pope Paul VI also discussed married love.
"This love is first of all fully human, that is to say, of the senses and of the spirit at the same time. It is not, then, a simple transport of instinct and sentiment, but also, and principally, an act of the free will, intended to endure and to grow by means of the joys and sorrows of daily life, in such a way that husband and wife become one only heart and one only soul, and together attain their human perfection.
Then, this love is total, that is to say, it is a very special form of personal friendship, in which husband and wife generously share everything, without undue reservations or selfish calculations. Whoever truly loves his marriage partner loves not only for what he receives, but for the partners's self, rejoicing that he can enrich his partner with the gift of himself." (Humanae Vitae, para 9)
In order to read the entire document, visit the website for the Vatican.