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Onan

Onan is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Onan rather than just read about it. In short: Onan was a figure detailed in the Book of Genesis chapter 38, as the second son of Judah and his Canaanite wife, the daughter of Shuah. Onan had an older brother Er and a younger brother, Shelah.

Onan — main illustration
Onan — illustration

Key takeaways

  • Onan belongs to biology; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Onan to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Onan from memory before moving on to harder problems.

Reference excerpt

Onan was a figure detailed in the Book of Genesis chapter 38, as the second son of Judah and his Canaanite wife, the daughter of Shuah. Onan had an older brother Er and a younger brother, Shelah. Onan was commanded by his father, Judah, to perform his duty as a husband's brother according to the custom of levirate marriage with Er's widow Tamar. Onan refused to perform his duty as a levirate and instead "spilled his seed on the ground whenever he went in" because "the offspring would not be his", and was thus put to death by Yahweh. This act is detailed as retribution for being "displeasing in the sight of Lord". Onan's crime is often misinterpreted as being masturbation, but it is universally agreed among biblical scholars that Onan's death is attributed to his refusal to fulfill his obligation of levirate marriage with Tamar by committing coitus interruptus.

Biblical account After Yahweh slew Onan's oldest brother Er, Onan's father Judah told him to fulfill his duty as a brother-in-law by entering into a levirate marriage with his brother's widow Tamar to give her offspring. Religion professor Tikva Frymer-Kensky has pointed out the economic repercussions of a levirate marriage: any son born to Tamar would be deemed the heir of the deceased Er and could claim the firstborn's double share of an inheritance. However, if Er were childless or only had daughters, Onan would have inherited as the oldest surviving son. When Onan had sex with Tamar, he withdrew before he ejaculated and "spilled his seed on the ground" thus committing coitus interuptus, since any child born would not legally be considered his heir. The next statement in the Bible says that Onan displeased Yahweh, so the Lord slew him. Onan's crime is often misinterpreted to be masturbation but it is generally agreed among biblical scholars that Onan's death is attributed to his refusal to fulfill his obligation of levirate marriage with Tamar by committing coitus interruptus. The regulation of levirate marriage in Deut 25:7–10 shows that the custom had encountered some opposition:

But if the man has no desire to marry his brother’s widow, then his brother’s widow shall go up to the elders at the gate and say, ‘My husband’s brother refuses to perpetuate his brother’s name in Israel; he will not perform the duty of a husband’s brother to me.’ Then the elders of his town shall summon him and speak to him. If he persists, saying, ‘I have no desire to marry her,’ then his brother’s wife shall go up to him in the presence of the elders, pull his sandal off his foot, spit in his face, and declare, ‘This is what is done to the man who does not build up his brother’s house.’ Throughout Israel his family shall be known as ‘the house of him whose sandal was pulled off.’ Halizah, the ceremony above, allowing a man to refuse his duty was a concession to the reluctance to comply with the custom.

Family tree

Interpretation

Early Jewish views One opinion expressed in the Talmud argues that this was where the death penalty's imposition originated. The Talmud also likens emitting semen in vain to shedding blood. However, the regulations concerning ejaculation in the book of Leviticus, whether as a result of sexual intercourse or not, merely prescribe a ritual washing and becoming ritually impure until the following evening.

Classical Christian views Early Christian writers have sometimes focused on the spilling seed, and the sexual act being used for non-procreational purposes. This interpretation was held by several early Christian apologists. Jerome, for example, argued:

But I wonder why he the heretic Jovinianus set Judah and Tamar before us for an example, unless perchance even harlots give him pleasure; or Onan, who was slain because he begrudged his brother his seed. Does he imagine that we approve of any sexual intercourse except for the procreation of children? Epiphanius of Salamis wrote against heretics who used coitus interruptus, calling it the sin of Οnan:

They soil their bodies, minds and souls with unchastity. Some of them masquerade as monastics, and their woman companions as female monastics. And they are physically corrupted because they satisfy their appetite but, to put it politely, by the act of Onan the son of Judah. For as Onan coupled with Tamar and satisfied his appetite but did not complete the act by planting his seed for the God-given [purpose of] procreation and did himself harm instead, thus, as [he] did the vile thing, so these people have used their supposed [female monastics], committing this infamy. For purity is not their concern, but a hypocritical purity in name. Their concern is limited to ensuring that the woman the seeming [ascetic] has seduced does not get pregnant—either so as not to cause child-bearing, or to escape detection, since they want to be honored for their supposed celibacy. In any case, this is what they do, but others endeavor to get this same filthy satisfaction not with women but by other means, and pollute themselves with their own hands. They too imitate the son of Judah, soil the ground with their forbidden practices and drops of filthy fluid and rub their emissions into the earth with their feet Clement of Alexandria, while not making explicit reference to Onan, similarly reflects an early Christian view of the abhorrence of spilling seed:

Because of its divine institution for the propagation of man, the seed is not to be vainly ejaculated, nor is it to be damaged, nor is it to be wasted. To have coitus other than to procreate children is to do injury to nature.

Roman Catholic views

The papal encyclical Casti connubii (1930) invokes this Biblical text in support of the teaching of the Catholic Church against contracepted sex by quoting St. Augustine, "Intercourse even with one's legitimate wife is unlawful and wicked where the conception of the offspring is prevented. Onan, the son of Juda [sic], did this and the Lord killed him for it."

… excerpt ends here. Continue reading the full article.

Illustrations

Onan: Story of Onan
Story of Onan

Worked examples

Example 1 — a first encounter with Onan

Start with the simplest possible case. Write down what Onan claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Onan before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Onan ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Onan

In research
Onan appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Onan in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Onan is common in secondary-school and first-year university syllabi. It links to neighbouring topics Book of Genesis people, Masturbation, Obsolete medical terms, so understanding it makes those chapters shorter.
In everyday life
Look for Onan outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Onan in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Onan means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Onan out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Onan in simple terms?

Onan was a figure detailed in the Book of Genesis chapter 38, as the second son of Judah and his Canaanite wife, the daughter of Shuah. Onan had an older brother Er and a younger brother, Shelah.

Why does Onan matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Onan?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Onan.

Tags

  • Book of Genesis people
  • Masturbation
  • Obsolete medical terms
  • Sexuality in the Bible
  • Tribe of Judah

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