WHAT IS A LOGIA

1 criteria is used to determine if one is a Logia, however, there is actually a 2nd Criteria; an Intangible-body is the 1st criteria while, the 2nd is whether this intangible-body is not originating from biological-organisms (e.g. Creatures or Plants):

• The DF must give the user a body that can bypass solid attacks.

  Logias can only be effectively hurt by Haki if no weakness to utilize (like Water to fight against Crocodile’s Sand-based Body).
  

  

• Based on “Observation” of all who are Logia, not only are they able to bypass physical attacks, they’re always related to forces of nature or by-products of forces of nature (excludes things naturally produced by organisms such as poison, venom, snot, etc.)
  

Enel
Turns into lightening which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Kizaru
Turns into light which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Aokiji
Turns into ice which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Akainu
Turns into magma which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Monet
Turns into snow which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Ace & Sabo
Turns into flames which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Crocodile
Turns into sand which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Caeser Clown
Turns into gas which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Caribou
Turns into a swamp/mud which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

Blackbeard
Turns into a black-hole which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks, but due to gravity, his body absorbs all attacks as pain nullifying his intangibility. More details below on why he’s a Black-hole and not Darkness (the absence of light).

He fits under this classification, but requires a brief explanation, his DF is the Darkness fruit. It’s easy to assume Oda means Darkness as in the absence of light which is the opposite of Kizaru, but that’s wrong, how? When you switch your lights off, does gravity increase? No, the DF name is a misnomer.

In space there’s something called a Black-hole, it can’t be seen which is why Oda portrays Blackbeard’s DF as darkness and this is why he can turn into darkness too. Another thing is Black-holes (the biggest ones) are found in the centre of galaxies, they can’t be seen but their effect to pull everything around it towards them can can be observed.

Blackbeard’s body is literally a Black-hole which is why his body absorbs all attacks as pain rather than bypass them.

Smoker
Turns into smoke which is produced by forces of nature (not organisms), his ability provides a body with ability to bypass solid attacks.

If one doesn’t possess all attributes of a Logia, then they’re not a Logia:

• Possess an ability that provides a body with ability to bypass solid attacks.
• Be produced by forces of nature (and never by an organism).

Pica
Doesn’t possess a body that bypasses solid attacks, though produced by forces of nature.

Whitebeard
Doesn’t possess a body that bypasses solid attacks, though produced by forces of nature.

Diamond Jozu
Doesn’t possess a body that bypasses solid attacks, though produced by forces of nature.

Shu
Doesn’t possess a body that bypasses solid attacks, though produced by forces of nature.

Magellan
Doesn’t possess a body that bypasses solid attacks and produced by organisms.

Trebol
Doesn’t possess a body that bypasses solid attacks, though produced by organisms (not forces of nature). Below I explain in more detail that he’s really not a solid.

• Why would Law tell someone that they won’t be able to reattach themselves? – It’s because they’re able to attach themselves back together.
• Why didn’t Law tell Tashigi that she won’t be able to reattach her body back together? – It’s because she remains detached when cut, she has a tangible body.
• Why didn’t he use the same cutting technique used on Vergo & Tashigi, against Trebol? – When he defeated Vergo, he cut him onto pieces with the same nameless technique he used for everyone else because it renders “them” (tangible bodied persons) incapacitated.
• Against Trebol, he uses? – Radio Knife and explicitly states that he won’t be attaching himself back together.

Oda has highlighted Logia as nature as one of the keywords. Also note in Oda’s response, Paramecia can change their own bodies as well (Trebol). – SBS Volume 35 (2004)

Pretty much confirming that Logia are natural being as earthquake can be considered natural, the only flaw is the lack of a body that bypasses solid attacks. – SBS Volume 58

Oda is talking about is none other than the renowned Vegapunk except there’s another professor of his calibre. He also says he will explain what Devil fruits are which should include their type. – SBS Voume 48