So, who invented the term “Celestial sex?"
Coexisting with these two deities was a limitless amount of cosmic spirit matter known as 'intelligence,' out of which Elohim and Heavenly Mother made countless spirit babies via celestial sex. —One Nation Under Gods, p. 285
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The quote illustrated above is a good example of how critics twist LDS beliefs into a form that makes them look ridiculous. Quotes made by early LDS leaders are often used to support the claim that Latter-day Saints believe in “Celestial sex.” It should be noted, however, that LDS leaders have never used the term "Celestial sex." This phrase was coined by critics of the Church, likely for its “shock value” in portraying the following concepts in LDS belief:
The belief that God the Father has a physical body.
The belief that there exists a Heavenly Mother who also possesses a physical body.
The belief that our Heavenly Father and Mother together are capable of creating “spirit children.”
Critics take these ideas and combine them, leading to a declaration that Latter-day Saints therefore believe in “Celestial sex.” Various anti-Mormon works then use this idea to mock LDS beliefs or shock their readers—though this claim does not describe LDS beliefs, but the critics' caricature of them.
The critics' ***umptions simply take what we know about our physical world and naively apply it to the afterlife. When one examines the critics’ point further, a key question ought to be raised: How does the union of two immortal beings in a physical manner produce spirit offspring? Latter-day Saint belief is that “spirit children” only receive a physical body upon being born on earth.
This question, of course, cannot be answered. It is pointless to speculate on the exact manner in which “spirit children” are produced, and to ***ume that this occurs through a process called “Celestial sex” is to apply a worldly mindset to a spiritual process.
The bottom line: Latter-day Saints do not know the mechanism by which “spirit children” are produced, and no LDS doctrine claims that "celestial sex" is the means.