This is one I've seen come up loosely in various topics and I am wondering what the general consensus is on it!

Intelligence.

Is this a measurement of how much your character knows, or is it a measure of how quickly they pick up new things? Is it innate, or learnt? Or something else?

The two ways I can see it are:

Intelligence is how much your character knows. A character who has spent years doing things and learnt how to do them well is intelligent.

Intelligence is how smart your character is innately. A character who knows nothing can be intelligent if they learn things quickly, and someone who has learnt a lot can have low intelligence if it took them hundreds of years to learn it (where it might take another less time).

What do you think? How do you view intelligence?

Mixture of knowledge, quick learning and logical analysis skills / abstract thinking.

I have RP some high INT characters that are very ignorant of most of the knowledge of the world but can figure things out fast.   

Generally I will have them not be proficient in the History/Arcana/Religion skills but rather Investigation/Insight/Survival  

I think it's both.

Let's look at the skills linked to Intelligence: Arcana, History, Investigation, Nature, Religion

Most of them seem to be knowledge skills, or how much you know, but Investigation is explicitly your skill in deducing meaning from clues.

"An Intelligence check comes into play when you need to draw on logic, education, memory, or deductive reasoning."

Other Intelligence Checks

The DM might call for an Intelligence check when you try to accomplish tasks like the following:

• Communicate with a creature without using words
• Estimate the value of a precious item
• Pull together a disguise to pass as a city guard
• Forge a document
• Recall lore about a craft or trade
• Win a game of skill

Actually ... come to think of it, I don't think Intelligence is about how much you know, but how well you remember and apply what you know. How much you know is story and background related, but how well you use that information is ability based.

I tend to go by the practical uses it has in skills etc. 

It's both recalling information/book smarts, from history/nature/relgiion and remembering complex wizard spells, and also how well you can put things together logically, like investigation. 

I don't necessarily tie to to how quickly you learn new skills though. At least not universally. 

In the real world, intelligence describes the ability to assimilate new knowledge and actually understand it, not just regurgitate facts. However, to make proper use of any knowledge gained one must retain said knowledge unless you're whipping out your phone and googling stuff every time you think about something so even if you don't ascribe information retention to pure intellect, having one without the other is like having a light bulb but no electricity. 

In D&D intelligence mechanically represents both the ability to learn and retain knowledge, as well as to make use of those two things together. The investigate skill represents all of this: observing facts and combining those facts with pre-existing knowledge to make a conclusion about the situation.

In my D&D, INT is all things directly related to information. That means gaining and recalling knowledge.

In contrast, WIS in my D&D is all about assessing the present situations. This doesn't mean learning for my D&D but, rather, discerning.

That's just me, though.

It's both. It's memory and learning. Learning is literally just "adding knowledge" and memory is "recalling knowledge". Both use Intelligence - both in real life and RAW. See the Using Each Ability section for Intelligence.

Intelligence is always useful in our games - it fuels several skills and can be used with most tools as well. Just make those skills/tools matter more if you want INT to have a bigger impact.

Intelligence is a character's memory, reasoning, learning ability outside of the written word. Wisdom is a character's common sense, enlightenment(spiritual light), judgement(to think or hold a decree, to decide), wile, will power(self control), intuitive(perception of truth fact independent of any reason, intuition). Intelligence that is high gives a Magic User a excellent eidetic memory? Yet he has trouble remembering spells ???

Quote from Kurus >>

Intelligence is a character's memory, reasoning, learning ability outside of the written word. Wisdom is a character's common sense, enlightenment(spiritual light), judgement(to think or hold a decree, to decide), wile, will power(self control), intuitive(perception of truth fact independent of any reason, intuition). Intelligence that is high gives a Magic User a excellent eidetic memory? Yet he has trouble remembering spells ???

 
Eidetic? No. That's a feat (Keen Mind).

However, preparing spells isn't simply memorising them. It's more complicated than that. It's more like partitioning a computer hard drive to dedicate memory towards a specific set of programs so the right tasks can be run. Except you're partitioning your mind. Manipulating reality is a bit more complicated than remembering a couple of words and waving a hand. The processes are more than that internally: it taxes the body and the mind. When you prepare a spell you're not just remembering some words, you're preparing a part of your mind for a big mental process that will be doing a lot of things all at once, while channeling that through words/gestures as you pull on reality and bend it, with thought and body. 

It can manifest in a number of ways. Academic knowledge, keen memory, reasoning skills, pattern recognition, mental processing speed, etc. I don't think you can really peg it as strictly one or the other.