The Malthusian theory of overpopulation is a popular doomsday prediction. Thomas Malthus (1766 -1834) proposed that population increases due to improved standards of living would lead to overpopulation, famine, disease and terrifying death rates. Yet, many countries that achieve the status of “developed nation” have falling birthrates–sometimes less than necessary to “replace” the parents, which could, in the future, create a very different population problem.
The first commandment found in the Torah is “p’ru u’rvu, be fruitful and multiply” (Genesis 1:28). The Gemara (Yevamot 61b) states: “A man shall not abstain from the act of propagation unless he already has children.” (The commandment of p’ru u’rvu applies to men, not women, because a woman cannot be commanded to perform a mitzvah that is life threatening, such as giving birth).
While the Torah commandment of p’ru u’rvu means trying for self-replacement, that is one son and one daughter, it is the rabbinic opinion that one should strive for more than the minimum, stating: “If a man married in his youth, he should marry again in his old age; if he had children in his youth, he should also have children in his old age; as it says (Ecclesiastes 11:6), “In the morning, sow your seed and in the evening do not withhold your hand; for you do not know which shall prosper...’” (Yevamot 62b).
The Prophet Isaiah declared: “He [God] formed [the world] to be inhabited" (Isaiah 45:18). God runs the world. When the Judean King Hezekiah refused to have children because he foresaw that one of his descendants would be exceedingly wicked, the Prophet Isaiah said: “What have you to do with the secrets of the All-Merciful? You should have done what you were commanded [i.e. have children], and let the Holy One, blessed be He, do that which pleases Him” (Talmud Berachot 10a).
*Note: Judaism does not suggest that one should have more children than is healthy for the parent(s). Therefore, Judaism allow for the use of birth control in certain limited circumstances, but that is a topic for another discussion.