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Can you use Minor Illusion to create an illusion of a working mirror, i.e. with a working reflection?

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According to the description:

You create a sound or an image of an object within range that lasts for the duration. The illusion also ends if you dismiss it as an action or cast the spell again.

If you create a sound its volume can range from a whisper to a scream. It can be your voice, someone else's voice, a lion roaring, a drum beating or any other sound you choose. The sound continues unabated throughout the duration or you can make discreet sounds at different times before the spell ends.

If you create an image of an object such as a chair, muddy footprints or a small chest-it must be no larger then a 5 Foot cube. The image can't create sound, light, smell or any other sensory effect. Physical interaction with the object reveals it to be an illusion, because things can pass through it.

With this in mind - I would say no. Minor Illusion is very limited (e.g. static), and cannot produce any side effects (e.g. no light, or other sensory effects). I expect this also means the light would pass through the illusion, and that maintaining the same properties as the physical version of the object is beyond the scope of the illusion. This is mostly because its not actually a real object (e.g. it does not behave like a mirror), it only looks like one.

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    \$\begingroup\$ Hmm... I'm not sure that the bolded text really applies to what's going on here. Mirrors don't create light, they reflect it. Besides, by this reasoning one could tell the difference between any illusion of a sufficiently reflective surface and the real thing (such as a polished helmet): no reflections! \$\endgroup\$
    – Tophandour
    Commented Mar 30, 2016 at 16:48
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    \$\begingroup\$ If light passed through an object then it would be invisible. Light bounces off of visible objects, that's what makes them visible. The only thing special about a mirror is that light is reflected at the angle of incidence, rather than being scattered randomly. \$\endgroup\$ Commented Mar 30, 2016 at 17:31
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    \$\begingroup\$ @JohnKugelman It's a valid argument, but nothing about the magic implies that it is actually visible (as in obeying the properties of physics re: reflecting/scattering photons), only that the unknowing perceive it to be real. It exists only in your mind, the illusionist is bending the light/weave in order to trick you, etc. Also, without going too deeply into physics.SE territory, keep in mind that light == matter, thus if things can pass through the illusion because it is not real, so too can light, lending further credence to the fact that the illusion doesn't actually exist. \$\endgroup\$ Commented Mar 30, 2016 at 20:47
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    \$\begingroup\$ @LegendaryDude Plus, viewers who know it's an illusion can see through it. That solidly torpedoes any argument that rests on assuming it reflects light like an independent object would. \$\endgroup\$ Commented Mar 30, 2016 at 22:54
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    \$\begingroup\$ Historical note: Earlier editions (some of them, anyway) made a clear distinction between illusions that existed only in characters' minds, and illusions that were more like holograms in that they existed in the world despite being intangible. The question of whether mirrors had reflections wasn't directly addressed, but knowing that both sorts of illusions had historical support might be useful to anyone making a ruling about this. \$\endgroup\$
    – GMJoe
    Commented Mar 30, 2016 at 23:33
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Yes, because physics.

The simple fact that you can see an illusion means it reflects light, whether it is the illusion of a mirror or not [edit: see below].

Note that this does not violate the rule that “The image can't create sound, light, smell or any other sensory effect.” The image is not emitting light, it is reflecting it. An illusion of a mirror would act no differently than the illusion of anything else - it just reflects the light perfectly, allowing the viewer to see an image.

Objects that do not reflect light (at all) look like a perfectly flat, black surface. So if illusions are to be useful in any way, they must reflect light.

[Edit]: I will concede that if illusions are a purely mental construct, like an hallucination, that physics will not apply; however, in that case my answer is still yes, because if we're tricking the mind we can surely trick it thoroughly.

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    \$\begingroup\$ You may want to expand your reasoning to establish a base argument that illusions cannot create the illusion of self-illumination, since it's generally accepted that they can do so, and your answer relies on the premise that they cannot. \$\endgroup\$ Commented Mar 30, 2016 at 17:51
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    \$\begingroup\$ +1 I wish more people understood that ALL visible objects reflect light... they just scatter it more randomly than a shiny object (like a mirror) does! \$\endgroup\$
    – Matthew
    Commented Mar 30, 2016 at 18:31
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    \$\begingroup\$ -1 Illusions do not need to obey the laws of physics. They are magic, and might as well be a figment of your imagination (because they quite literally are). \$\endgroup\$ Commented Mar 30, 2016 at 20:52
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    \$\begingroup\$ @Escoce By that logic, illusions wouldn't change in appearance due to changes in lighting - which means you could detect any illusion just by holding a candle to it. This seems weird to me. So many illusions that adventurers encounter are in dark dungeons, and in dark dungeons adventurers carry light sources. Every illusion would stand out like a sore thumb due to remaining unilluminated even when the adventurers approach it, or by being illuminated in a dark place even before they approach. \$\endgroup\$
    – GMJoe
    Commented Mar 30, 2016 at 23:43
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    \$\begingroup\$ +1. The only ways to see an illusion are that a) it reflects light so your eyes can see it, b) it generates light so your eyes can see it (specifically contradicted by the rule), or c) it's a totally a figment in peoples' mind mimicing a real object, in which case a mirror would act like you expect a mirror to. \$\endgroup\$
    – mxyzplk
    Commented Mar 31, 2016 at 2:35
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No.

There are two ways you could think about the reflection. You could imagine it as an effect created by the caster - a constant modification in reaction to the movement of objects around the "mirror" - but that would imply the constant attention of the caster. But that stands in contradiction to the fact that the spell does not require concentration. (It doesn't seem that any motion in the visual images is allowed, although some flexibility with sound illusions is given.)

Alternatively, you could imagine that the image has the property of being able to reflect light - that is, it is a physical mirror. But this is a physical interaction, and "Physical interaction with the image reveals it to be an illusion, because things can pass through it." This may seem a little strange, since we intuitively assume that we can perceive illusions in the same physical way that we perceive actual objects - that is, ambient light reflects from the surface of the illusion and reaches our eyes. But this intuition is apparently wrong. Illusions do not reflect ambient light - if we discern the illusion it becomes faint to our sight, so clearly most or all ambient light actually passes through the illusion. Furthermore, different observers may see different images, depending on whether they discern the illusion, so the process cannot be as deterministic as conventional science would demand. The physics are not explained, but clearly they are different from what we are used to in the mundane world.

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  • \$\begingroup\$ You cannot take "physically interact" to mean "view light reflected off it". If you said you physically interacted with a car but you only looked at it, they'd conclude you lied to them. \$\endgroup\$
    – TREB
    Commented Jun 13 at 22:26
  • \$\begingroup\$ @TREB I didn't say that we are interacting with a car. I said we are interacting with the light, which is clearly true. \$\endgroup\$
    – pokep
    Commented Jul 9 at 15:20
  • \$\begingroup\$ This is just assuming that "physical interaction" mean "interaction related to the science of physics". Rather than physical in the sense of solid objects making contact rather than sound or light. \$\endgroup\$
    – TREB
    Commented Jul 10 at 16:58
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I am going to say no, and here is why.

Minor illusion allows you to mimic simple things. However it does not duplicate effects. Although a mirror is a simple thing, the images it reflects are or could be very complicated. Additionally, they'd need to mimic what's being reflected in mirror image.

I think you could use minor illusion to mimic a portrait, but s mirror I think is too complicated.

Ok, I am pulling out the boom to refine my answer, but that's this is still the basis.

Update: nevermind, shadow players answer is good.

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No, one cannot create a mirror illusion with this spell, because reflection requires matter interacting with light-stuff (called photons in our reality) and the collision causes them to change direction (which we call either reflection or refraction depending on how focused the effect is). While several of the answers above point out that illusions are visible, I would like to humbly point out that illusions are a form of magic often relegated to a school centered on light-production and light-manipulation, not creating matter that then interacts with light on its own.

If I conjure a brown wooden table, then that table reflects brown light while absorbing other hues. When the lights go out the table has no light to reflect, so it is, for all intents and purposes, impossible to see. However, an illusory table is not solid like the conjured one; it is a preprogrammed construction of light that is specifically defined as impossible for matter to interact with. That would mean it cannot reflect or absorb light; light passes through it and it is technically transparent. The only reason we can see it is because it is producing light.

The way I read the description, at the time of casting the spell, the caster must decide exactly what they wish to present, and that is the amount of continuous light the object produces. Not only would such an illusion be easily spotted due to a lack of reflection, any change in the lighting of the room would not cause the object to lighten or darken – it would stand out because it is fundamentally incapable of reacting to its environment in the way actual matter is. In a dark room therefore it would glow.

This does however raise several mechanical issues. Any and all light that would come into contact with the object instead passes through it. So if I simulate a five foot box then I can see within the box using light that passes through the illusion from outside, but I cannot see what is outside. Likewise if I light a torch within the box then those outside will see the box emitting torchlight from within. I believe a similar issue arose when my group contemplated the possibility of an invisible light source. You see exactly what the spell says you can see (in this instance whatever the caster decided upon at casting time) and then apply lighting effects as if the spell were not in effect.

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    \$\begingroup\$ So... You're saying the rules for illusions don't make sense and are contradictory? \$\endgroup\$
    – GMJoe
    Commented Mar 31, 2016 at 4:58
  • \$\begingroup\$ No, I believe I said that the rules for illusions say that, unless otherwise specified, they are light-based constructions that do not interfere with matter or light in any discernible way. An illusion of a blindfold prevents you from seeing through it, but not from being hurt by looking at the sun, because light passes through it. \$\endgroup\$
    – Benjamin
    Commented Mar 31, 2016 at 15:55
  • \$\begingroup\$ Although, now that I think about it, my interpretation of the spell does not mean that matter cannot interact with the illusion, simply that matter passes through it. This would make for some very interesting (and hard for a GM to describe) visual effects when an illusion interacts with an actual mirror or prism. While the objects technically pass through they also can interact with the light-stuff. \$\endgroup\$
    – Benjamin
    Commented Mar 31, 2016 at 16:20
  • \$\begingroup\$ You say "at the time of casting the spell, the caster must decide exactly what they wish to present, and that is the amount of continuous light the object produces." The spell specifically cannot create light. \$\endgroup\$ Commented Mar 31, 2016 at 16:59
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    \$\begingroup\$ @Benjamin Sorry, I'm confused by the apparent contradiction between the phrases "one cannot create a mirror... because reflecting light requires interacting with light-stuff" and "illusions are... centered on light-production and light-manipulation", and your section on mechanical issues seems to specifically highlight a number of points that don't make sense if you use the rules interpretation you describe, as they would result in illusions being easier to detect than the rules say they are. I'm probably missing some part of your reasoning. \$\endgroup\$
    – GMJoe
    Commented Mar 31, 2016 at 23:24

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