Matt Fradd
Spirituality/Belief • Books • Writing
What I Should Have Said to Dennis Prager about The Sin of Onan
April 25, 2023
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In my recent conversation with Dennis Prager, the subject of masturbation came up. 

Prager said that since masturbation is nowhere condemned in the Old or New Testaments, this serves as evidence that masturbation is not a sin. 

This is what is called an argument from silence, where a conclusion is based upon silence or lack of evidence. Such arguments aren’t always illegitimate, but they are notoriously weak and inconclusive. The Bible also does not condemn insider trading and chattel slavery, for example, but Prager would condemn these as sins.

Prager also responded preemptively to something he suspected I might bring up—the sin of Onan:

Judah took a wife for Er his firstborn, and her name was Tamar. But Er, Judah’s first-born, was wicked in the sight of the Lord; and the Lord slew him. 

Then Judah said to Onan, “Go in to your brother’s wife, and perform the duty of a brother-in-law to her, and raise up offspring for your brother.” But Onan knew that the offspring would not be his; so when he went in to his brother’s wife he spilled the semen on the ground, lest he should give offspring to his brother. And what he did was displeasing in the sight of the Lord, and he slew him also (Gen. 38:6-10).

This passage involves the Hebrew custom of levirate marriage, according to which, if a man died childless, it was his brother’s duty to marry the widow and father children who would be legally regarded as sons of the dead man. It is called levirate marriage since levir is the Latin term for brother-in-law, and the woman’s brother-in-law is the biological father of the children.

Onan did not wish to father children for his dead brother, but he did want to have sexual pleasure from the widow, so he practiced coitus interruptus to avoid inseminating her—allowing him the pleasure of sex with the woman but preventing him from fathering children for his brother.

This passage has been used by many Christians as a prooftext against deliberately rendering the sexual act infertile, which includes masturbation.

However, Prager made the case that Onan was punished not for “spilling his seed” but for violating the levirate marriage custom.

At the time of my discussion with Prager, I wasn’t equipped to respond to this objection in the heat of the moment, and so I addressed his objection from a natural law perspective. Namely, we can know by reason what sex is for (union and procreation), and to deliberately thwart the end of sex is a perversion. 

While it can be tricky to discern the nuances of what was in the mind of a biblical author writing 3,000 years ago, if I could engage Prager on this again, I would make these points:

 

1. Prager Is at Odds with Other Jews

Prager is at odds with the respected Jewish commentary, Bereishis: Genesis which states:

[Onan] misused the organs God gave him for propagating the race to unnaturally satisfy his own lust, and he was therefore deserving of death (5:1677).

 

2. The Penalty Is Far Less Severe in the Mosaic law

If Prager was correct and Onan was struck dead by God for refusing to give offspring to his deceased brother’s wife, why isn’t the death penalty applied to other cases where a man refuses to fulfill the duty of a brother-in-law?  The penalty announced by the Mosaic law isn’t death but merely public humiliation. If a man refuses to perform the duty, then:

His brother’s wife shall go up to him in the presence of the elders and pull his sandal off his foot and spit in his face. And she shall answer and say, “So shall it be done to the man who does not build up his brother’s house.” And the name of his house shall be called in Israel, “The house of him who had his sandal pulled off” (Deut. 25:9-10). 

The fact that the Mosaic law required public humiliation for failing to fulfill the responsibility—but Onan was put to death—indicates that Onan was guilty of more than just failing to fulfill the responsibility. There was something immoral about the sexual acts that he performed with the woman. 

Thus, the text says that “what he did [i.e., the sex acts with coitus interruptus] was displeasing in the sight of the Lord.” It does not say “what he did not do [i.e., give children to his brother]” was what earned him death. The latter failure would only have warranted public humiliation according to God’s law through Moses. The way the text presents matters, it’s what Onan did do, not what he didn’t do, that caused his death.

 

3. The Use of Graphic Language

Hebrew contains several ways of referring to the sexual act—to “know,” to “go in to,” and to “lie with.” The first of these is the most decorous and normally refers to lawful, wholesome sexuality (e.g., “Adam knew Eve his wife,” Gen. 4:1). The latter two are more blunt and can refer to both lawful and unlawful sex.

In Genesis 38, we go beyond these simple descriptions, and we are told the precise details of what Onan did: “When he went in to his brother’s wife he spilled the semen on the ground.” This unexpected intrusion of the graphic details of what Onan did calls attention to the specific thing that he did wrong. As Fr. Brian Harrison notes:

If the inspired author, while knowing the same historical facts, had evaluated them in the way most modern exegetes would have us believe he did (with moral indifference toward Onan’s contraceptive act as such), we would expect quite different wording. “Spilling the seed,” being irrelevant to the author’s interest and purpose on that hypothesis, would not even have been mentioned. Instead, we would expect to be faced with an account stating more discreetly that, even though Onan took Tamar legally as his wife, he refused to allow her to conceive, so that God slew him for his “hardness of heart,” his pride, or perhaps his avarice (in wanting his brother’s property to pass to himself and his own sons) (The Real Sin of Onan).

 

4. Natural Law

We also should consider what happened from the perspective of natural law—that is, what a reasonable person would conclude based on human nature.

One way of applying this to the current situation is to simply ask, “What are human genitals supposed to do? What’s their function?”

The answer is obvious. They have two functions: eliminating waste (urine) and facilitating reproduction (directly, through the transmission of semen, and indirectly, through uniting the spouses). These are their obvious, proper uses.

Therefore, if you’re doing something else with your genitals—or if you deliberately keep them from fulfilling their proper uses, as Onan did—then you are misusing them by definition.

 

5. Protestants Should Agree With Catholics

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"It is better to be a child of God than king of the whole world!"
St. Aloysius Gonzaga

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“Our own guardian angel [is] for each of us like a trustworthy captain commissioned to defend a stronghold against its enemies. Our guardian angel remains alert and watchful lest any foes should capture and occupy the fort of our soul. These angels are the faithful guards whom the Lord has located on the walls of Jerusalem to keep watch over His flock throughout the night lest the ferocious wolf of hell, who prowls around like a roaring lion seeking for someone to devour, should seize upon our poor souls!”
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Ephesians 2:8-10

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Life is very, very simple, actually.

There is a lot going on. We are confused about many things. Embarrassed that we are confused. Pretend not to be. Have a few soundbites we can rely on when the conversation turns to Trump or the state of the Church or what is going on in Israel and Gaza or the AI revolution. We hope they don’t press us because we know enough to answer two or three questions before they will hit bedrock and we will have nothing.

All of this can lead us to believe the lie that life is complicated. And since we cannot figure it out, we should either quit, or numb, or pretend, or run ourselves ragged trying to understand everything we think we should understand.

And yet life is simple. Very, very simple. There is very little to figure out.

Love what is good. Hate what is evil. But how? When I have willingly habituated myself to do the opposite. Pray. Repent. Keep turning away from distractions. Don’t hate yourself for failing. Hope in the good God who is better than you think He is. Who cares for you more than you think He does.

What are your duties? Do them with joy and attention. Don’t hate yourself when you fail at this. Pray. Repent. Have a sense of humor about your littleness. You are incredibly loved after all, remember?

Turn away from what is useless and petty and vulgar and think about what is excellent.

Say “Your will be done” 100 times a day, especially when things are bad or seem meaningless. Your headache. Your bad night sleep. The house you can’t seem to get around to tidying.

Be patient and gentle with stupid people who can’t seem to make themselves love or want to love what is good, yourself first and foremost.

Jesus, help me want to want to love you. Help me want to want to hate anything opposed to you or your kingdom.

Seek first the kingdom of God and his righteousness, and all these things will be added to you.
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Is Knowledge Possible (No ... And Yes)

I want to begin by admitting that I’m an amateur when it comes to epistemology. I do have a master’s degree in philosophy, but epistemology wasn’t my area of focus. Some of you reading this will know more about the subject than I do. And to be honest, I’m a little nervous about the comments. There’s a good chance that if you engage with what I’m about to say in any real depth, I won’t understand you and it will be my fault that I don’t.

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We've long assumed that knowledge requires three criteria: (1) belief, (2) truth, and (3) justification. In other words, to know something is to believe it, for it to be true, and to have good reason for believing it. That’s the classical definition: justified true belief (JTB).

And just real quick, if you’re wondering why knowledge can’t be defined by just the first two criteria, it’s because believing something that happens to be true is more like getting lucky than knowledge. Imagine I say it’s raining in Adelaide, but I have no reason for thinking so. I didn’t check my weather app or ask anyone who lives there. If it turns out that it is raining, I was right, but only by chance. That’s not knowledge. To genuinely know something, you need more than belief and truth, you need a reason for thinking it’s true. You need justification.

Okay …

Along Comes Gettier

Now, for a long time, this three-part definition held up well. But then, in 1963, Edmund Gettier came along and broke everything in three pages. You can read that paper here.

Gettier presented scenarios where someone has a belief that is both true and justified, yet we still hesitate to call it knowledge. Why? Because the belief turns out to be true by accident.

One of the most well-known examples (though not from Gettier himself but often used to illustrate his point) is the case of the stopped clock. A man glances at a clock that has stopped working, sees that it says 2:00, and forms the belief that it is 2:00. And it just so happens to be 2:00. His belief is true. He used a normally reliable method, checking the time on a clock. And yet, the method failed. The belief was correct purely by coincidence.

Can We Save “Knowledge”

Now, some have tried to save the classical definition by saying, “Well, that wasn’t really justified. The clock was broken, so the belief was faulty from the start.” But that kind of move just shifts the problem. If we start redefining justification every time we hit a weird case, we risk making it so strict that it no longer resembles what anyone would call a “justified belief.”

Others, like Alvin Goldman, proposed ditching the concept of justification entirely. Maybe knowledge isn’t about having reasons, but about using processes that generally lead to truth. This is called reliabilism: if your belief comes from a trustworthy process (like vision, memory, or scientific inference) it counts as knowledge.

But again, the clock case poses a problem. Even if the process is usually reliable, it clearly failed here. So are we back to calling this knowledge, even though it was true by luck?

Still others have suggested that knowledge is less about having the right reasons or processes, and more about the person doing the knowing. This is what’s known as virtue epistemology: the idea that knowledge is a kind of intellectual success rooted in intellectual virtue: careful thinking, honesty, openness to evidence. On this view, knowing isn’t about checking boxes; it’s about doing something well. Like an archer hitting the bullseyes, not by accident, but through skill.

That’s compelling. But even here, questions linger. How do we measure intellectual virtue? And isn’t it still possible to do everything right and end up wrong—or to be wrong for the right reasons and still, somehow, stumble into truth?

An (Initially) Unsettling Realization

Which brings me to a more unsettling thought.

If a belief like “it’s 2:00” can be true, feel justified, come from a reliable process, and still be the product of a broken clock—what else might we be getting wrong without realizing it? Maybe the deeper problem is that we can always be deceived. Even our best faculties (sight, memory, reason etc.) can betray us. And if that’s the case, maybe knowledge (at least in the strong, philosophical sense) is impossible. Or if not impossible, impossible to know if and when you have it.

David Hume once said, “A wise man proportions his belief to the evidence.” That strikes me as a sane and honest approach. The question isn’t whether I can be absolutely certain about what I believe, but whether I have good reasons for believing it—and whether I’m open to changing my mind if those reasons fall apart.

Some might find it unsettling—even scandalous—that we can’t achieve a God’s-eye view of the world. But honestly, what’s strange isn’t that we can’t see things with perfect clarity. It’s that we ever thought we should.

Maybe that’s why I find myself leaning toward fallibilism—the view that we can still know things, even while admitting we might be wrong. That kind of knowledge isn’t rigid or absolute, but humble and revisable. And that, to me, feels much closer to the way real life works.

So no, I’m not sure we need to cling too tightly to the word knowledge, at least not in the abstract, capital-K sense. What matters more is the posture we take toward the truth. That we pursue it carefully, honestly, and with a readiness to revise our beliefs when the evidence calls for it.

At least, that’s what I think I know.

 
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