user23662: 
If he wants, he remains percipient of loathsomeness in the presence of what is not loathsome. If he wants, he remains percipient of unloathsomeness in the presence of what is loathsome. If he wants, he remains percipient of loathsomeness in the presence of what is not loathsome & what is. If he wants, he remains percipient of unloathsomeness in the presence of what is loathsome & what is not. If he wants—in the presence of what is loathsome & what is not—cutting himself off from both, he remains equanimous, alert, & mindful. Or he may enter & remain in the beautiful liberation.
SN 46.54

Could someone explain what all this loathsome and unloathsome business is?

user10100: 
If he wants, he remains percipient of loathsomeness in the presence of
what is not loathsome.

The noble one can attain Loving Kindness Absorb-Jhana or Four Elements Almost-Absorb-Jhana, unloathsomeness, by photographic mental seeing loathsomeness-object such as human.
This is showing the proficiency of the meditation of the noble one.

If he wants, he remains percipient of unloathsomeness in the presence
of what is loathsome.

The noble one can attain loathsomeness-Absorb-Jhana or insight meditation, loathsomeness, by photographic mental seeing unloathsomeness-object such as things which the ordinary love to see, hear, smell, taste, touch, and think of.
This is showing the proficiency of the meditation of the noble one.

If he wants, he remains percipient of loathsomeness in the presence of
what is not loathsome & what is.

The noble one can attain Four Elements Almost-Absorb-Jhana, unloathsomeness, by photographic mental seeing loathsomeness-object or unloathsomeness-object (above).
This is showing the proficiency rapidly of the meditation of the noble one.

If he wants, he remains percipient of unloathsomeness in the presence
of what is loathsome & what is not.

The noble one can attain loathsomeness-Absorb-Jhana or insight meditation, loathsomeness, by photographic mental seeing loathsomeness-object or unloathsomeness-object (above).
This is showing the proficiency rapidly of the meditation of the noble one.

If he wants—in the presence of what is loathsome & what is not—cutting
himself off from both, he remains equanimous, alert, & mindful.
Or he may enter & remain in the beautiful liberation.

This is showing the proficiency rapidly of all above meditations of the noble one. They can close all sense-doors, protecting doors from unwholesome mind moment, by focus their wholesome mind moment on the meditation-objects until attain Jhana.
See DN10 SubhaSutta and MN 119 Kāyagatāsatisutta for some detail.
There also the explanation by ven MahaSariputta in Sutta. Khu. Paṭisambhidāmaggo

user8157: The relevent Pali word is "paṭikūla", which means "repulsive", as follows:

In the same way, when a mendicant has not developed or cultivated mindfulness of the body, their eye pulls towards pleasant sights, but is put off [repulsed] by unpleasant sights. Their ear … nose … tongue … body …
Evameva kho, bhikkhave, yassa kassaci bhikkhuno kāyagatāsati abhāvitā abahulīkatā, taṁ cakkhu āviñchati manāpiyesu rūpesu, amanāpiyā rūpā paṭikūlā honti …pe…
mind pulls towards pleasant thoughts, but is put off by unpleasant thoughts.
mano āviñchati manāpiyesu dhammesu, amanāpiyā dhammā paṭikūlā honti.
SN 35.247

The teaching in SN 46.54 is found in many places, such as in MN 152. It simply means the very skilled practitioner can view the repulsive in the repulsive, the unrepulsive in the repulsive, etc, etc, or have equanimity.
For example, monks & nuns are taught to view what is repulsive in the opposite sex. Therefore, a monk, for example, may view what is repulsive in a woman. However, a monk may also view what is not repulsive in a woman, such as women care for their children and also particularly care for monks, such as offering monks alms food. Or a monk may view a woman as merely five aggregates, which inclines to equanimity.
Why would one do such things?

Meditation upon the repulsive eliminates defilements connected to lust.

However, there is a sutta were many monks ended their life due to too much meditation upon the repulsive.

Therefore, meditation upon the non-repulsive is done to balance the mind plus develop wholesome qualities such as gratitude & loving-kindness.


All of the above are related to perceiving reality clearly.

23662: <blockquote>
<p>If he wants, he remains percipient of loathsomeness in the presence of what is not loathsome. If he wants, he remains percipient of unloathsomeness in the presence of what is loathsome. If he wants, he remains percipient of loathsomeness in the presence of what is not loathsome &amp; what is. If he wants, he remains percipient of unloathsomeness in the presence of what is loathsome &amp; what is not. If he wants—in the presence of what is loathsome &amp; what is not—cutting himself off from both, he remains equanimous, alert, &amp; mindful. Or he may enter &amp; remain in the beautiful liberation.<br />
<a href="https://www.accesstoinsight.org/tipitaka/sn/sn46/sn46.054.than.html" rel="nofollow noreferrer">SN 46.54</a></p>
</blockquote>
<p>Could someone explain what all this loathsome and unloathsome business is?</p>
 10100: <blockquote>
<p>If he wants, he remains percipient of loathsomeness in the presence of
what is not loathsome.</p>
</blockquote>
<p>The noble one can attain Loving Kindness Absorb-Jhana or Four Elements Almost-Absorb-Jhana, unloathsomeness, by photographic mental seeing loathsomeness-object such as human.</p>
<p>This is showing the proficiency of the meditation of the noble one.</p>
<blockquote>
<p>If he wants, he remains percipient of unloathsomeness in the presence
of what is loathsome.</p>
</blockquote>
<p>The noble one can attain loathsomeness-Absorb-Jhana or insight meditation, loathsomeness, by photographic mental seeing unloathsomeness-object such as things which the ordinary love to see, hear, smell, taste, touch, and think of.</p>
<p>This is showing the proficiency of the meditation of the noble one.</p>
<blockquote>
<p>If he wants, he remains percipient of loathsomeness in the presence of
what is not loathsome &amp; what is.</p>
</blockquote>
<p>The noble one can attain Four Elements Almost-Absorb-Jhana, unloathsomeness, by photographic mental seeing loathsomeness-object or unloathsomeness-object (above).</p>
<p>This is showing the proficiency rapidly of the meditation of the noble one.</p>
<blockquote>
<p>If he wants, he remains percipient of unloathsomeness in the presence
of what is loathsome &amp; what is not.</p>
</blockquote>
<p>The noble one can attain loathsomeness-Absorb-Jhana or insight meditation, loathsomeness, by photographic mental seeing loathsomeness-object or unloathsomeness-object (above).</p>
<p>This is showing the proficiency rapidly of the meditation of the noble one.</p>
<blockquote>
<p>If he wants—in the presence of what is loathsome &amp; what is not—cutting
himself off from both, he remains equanimous, alert, &amp; mindful.</p>
<p>Or he may enter &amp; remain in the beautiful liberation.</p>
</blockquote>
<p>This is showing the proficiency rapidly of all above meditations of the noble one. They can close all sense-doors, protecting doors from unwholesome mind moment, by focus their wholesome mind moment on the meditation-objects until attain Jhana.</p>
<p>See DN10 SubhaSutta and MN 119 Kāyagatāsatisutta for some detail.</p>
<p>There also the explanation by ven MahaSariputta in <a href="https://84000.org/tipitaka/read/roman_read.php?B=31&amp;A=11835" rel="nofollow noreferrer">Sutta. Khu. Paṭisambhidāmaggo</a></p>
 8157: <p>The relevent Pali word is &quot;paṭikūla&quot;, which means &quot;repulsive&quot;, as follows:</p>
<blockquote>
<p>In the same way, when a mendicant has not developed or cultivated mindfulness of the body, their eye pulls towards pleasant sights, but is <strong>put off</strong> [<strong>repulsed</strong>] by unpleasant sights. Their ear … nose … tongue … body …</p>
<p>Evameva kho, bhikkhave, yassa kassaci bhikkhuno kāyagatāsati abhāvitā abahulīkatā, taṁ cakkhu āviñchati manāpiyesu rūpesu, amanāpiyā rūpā <strong>paṭikūlā</strong> honti …pe…</p>
<p>mind pulls towards pleasant thoughts, but is <strong>put off</strong> by unpleasant thoughts.</p>
<p>mano āviñchati manāpiyesu dhammesu, amanāpiyā dhammā <strong>paṭikūlā</strong> honti.</p>
<p><a href="https://suttacentral.net/sn35.247/en/sujato?layout=linebyline&reference=pts&notes=asterisk&highlight=true&script=latin" rel="nofollow noreferrer">SN 35.247</a></p>
</blockquote>
<p>The teaching in SN 46.54 is found in many places, such as in MN 152. It simply means the very skilled practitioner can view the repulsive in the repulsive, the unrepulsive in the repulsive, etc, etc, or have equanimity.</p>
<p>For example, monks &amp; nuns are taught to view what is repulsive in the opposite sex. Therefore, a monk, for example, may view what is repulsive in a woman. However, a monk may also view what is not repulsive in a woman, such as women care for their children and also particularly care for monks, such as offering monks alms food. Or a monk may view a woman as merely five aggregates, which inclines to equanimity.</p>
<p>Why would one do such things?</p>
<ul>
<li><p>Meditation upon the repulsive eliminates defilements connected to lust.</p>
</li>
<li><p>However, there is a sutta were many monks ended their life due to too much meditation upon the repulsive.</p>
</li>
<li><p>Therefore, meditation upon the non-repulsive is done to balance the mind plus develop wholesome qualities such as gratitude &amp; loving-kindness.</p>
</li>
</ul>
<p>All of the above are related to perceiving reality clearly.</p>
