# Two Is One, And One Is None

#### desert.snake

##### Flashlight Enthusiast
In the morning, the thought arose that if a person following this rule has 2 flashlights with him and is asked how many lanterns he has, he will answer that 1. If he has 3 physical lanterns with him, then he will also have to answer, that he has 1 lantern, since 2 = 1 and 1 = 0. If he has 4 lanterns, then he will answer that he has 2 lanterns. If he has 5 lanterns, then he will also answer that he has 2 lanterns. It turns out that odd numbers do not exist, but there are only even numbers in this formula. What about physical lanterns that do not fall into this formula?

If a person has only 1 lantern, and he is asked about the presence of a lantern and he answers that he does not have lanterns, is he lying?

#### fulee9999

##### Enlightened
not necessarily, if he's counting in the plane of complex numbers he might have 1+ i4​ flashlights, but not saying the complex part, than the 1=0 but the complex part comes down to i4​=1, so while in normal form he has 2 flashlights, because of the rule of 1 he has zero, but because of complex numbers he has one.
QED.

#### kerneldrop

##### Flashlight Enthusiast
If a person has only 1 lantern, and he is asked about the presence of a lantern and he answers that he does not have lanterns, is he lying?

The ole Collatz conjecture of the flashlight world

The goal is to avoid detection and minimize interaction. Lanterns on handguns always count as 0 and it gets awkward when you just whip out a G29 with a light on it.

#### bykfixer

##### Flashaholic
For me price matters.
A \$25 item, yeah two is one.
A \$25,000 item one will have to do.

#### aznsx

##### Flashlight Enthusiast
I use the industry standard expression:

N+1

No muss, no fuss, no ambiguity, and no complex math, either. Redundancy does not require Nx2. It requires 1 more than the number required for functionality.

Keep it simple (as they say).

#### hamhanded

##### Enlightened
I use the industry standard expression:

N+1

No muss, no fuss, no ambiguity, and no complex math, either. Redundancy does not require Nx2. It requires 1 more than the number required for functionality.

Keep it simple (as they say).
Does it? I would expect caving party of 4, for example, to have more than 5 light sources among them.

Of course, for many people (myself included) in everyday scenarios, carrying even 1 dedicated flashlight starts to approach overpreparedness.

#### aznsx

##### Flashlight Enthusiast
Does it? I would expect caving party of 4, for example, to have more than 5 light sources among them.

Of course, for many people (myself included) in everyday scenarios, carrying even 1 dedicated flashlight starts to approach overpreparedness.

I wouldn't have thought it necessary to specify this, but being CPF, I guess it is.

My post was made in the context of the needs of an individual user with high-reliability requirements.

If you're talking about a multi-party group of people, each requiring high reliability, each would adhere to this redundancy principle individually.

...and just for the record, this (N+1) is indeed "industry standard" for basic functional redundancy in designing for reliability. I didn't come up with this myself (I'm not that smart). I understand it because I've learned it while working in that field a lot. Reliability engineering and redundancy designs get a lot more complex than this, but this (N+1) is the most basic level / technique. It's 'standard' enough you can google it to understand it and explore the subject of redundancy and reliability engineering in greater depth. That said, I think it's far less convoluted and ambiguous and is easier to understand than the expression that seems so popular in the flashlight community.

I agree with your math. Five cavers would indeed require more than 6 flashlights for the entire party. In such a situation / environment, they would each require no less than 2, so there would be at least 10 flashlights in that cave.

Just to further clarify: This applies to critical applications. If one's needs and requirements do not fall into that category, then this doesn't apply. I carry only one flashlight in my pocket when I'm at home.

#### nbp

##### Flashaholic
N is the number of flashlights you currently own; N+1 is the number you need.

#### aznsx

##### Flashlight Enthusiast
N is the number of flashlights you currently own; N+1 is the number you need.
Yes, the formula works for that too

#### hamhanded

##### Enlightened
I wouldn't have thought it necessary to specify this, but being CPF, I guess it is.

My post was made in the context of the needs of an individual user with high-reliability requirements.

If you're talking about a multi-party group of people, each requiring high reliability, each would adhere to this redundancy principle individually.

...and just for the record, this (N+1) is indeed "industry standard" for basic functional redundancy in designing for reliability. I didn't come up with this myself (I'm not that smart). I understand it because I've learned it while working in that field a lot. Reliability engineering and redundancy designs get a lot more complex than this, but this (N+1) is the most basic level / technique. It's 'standard' enough you can google it to understand it and explore the subject of redundancy and reliability engineering in greater depth. That said, I think it's far less convoluted and ambiguous and is easier to understand than the expression that seems so popular in the flashlight community.

I agree with your math. Five cavers would indeed require more than 6 flashlights for the entire party. In such a situation / environment, they would each require no less than 2, so there would be at least 10 flashlights in that cave.

Just to further clarify: This applies to critical applications. If one's needs and requirements do not fall into that category, then this doesn't apply. I carry only one flashlight in my pocket when I'm at home.
I wasn’t trying to be an ***, I apologize if it came across that way.

#### aznsx

##### Flashlight Enthusiast
I wasn’t trying to be an ***, I apologize if it came across that way.

Nahh, just wanted to clarify for the record. I didn't assume you were being an a** - I know better

#### Monocrom

##### Flashaholic
No one but a normie would ask how many lights I have on me. Therefore, I shall answer in the language they speak. Therefore, if I have three lights on me, I respond with "Three."

Anything else would simply confuse them.

#### Chauncey Gardiner

##### Flashaholic
😔 ........ sometimes I leave the house with only my cellphone.

I'll show myself the way out. 😞

#### kerneldrop

##### Flashlight Enthusiast
Today my wife proved this mantra while she was at work.

One quit working.
She pulled out a 2nd and used it until the battery died.
Then pulled out the 3rd and finished what she was doing.

#### Monocrom

##### Flashaholic
😔 ........ sometimes I leave the house with only my cellphone.

I'll show myself the way out. 😞
Get you a keychain light to put on your keychain.

#### Chauncey Gardiner

##### Flashaholic
Get you a keychain light to put on your keychain.
HA! I forgot that one .... do I get to count it?

"HELLO BOYS! I'M BACK! Where are the white women?"

Yes!

#### nbp

##### Flashaholic
Today my wife proved this mantra while she was at work.

One quit working.
She pulled out a 2nd and used it until the battery died.
Then pulled out the 3rd and finished what she was doing.

😂