Personality

What is an inclination? An inclination when one has a psychological tendency toward something.
An inclination can be for or against things. We can have an inclination towards something, or an inclination away from something - similar indeed to a like or a dislike respectively. In other terms, an inclination may urge us to seek or avoid the object of our inclination.
Synonyms: Disposition, like/dislike, bias, propensity, temperament

Personality is NOT just that which is inclined toward, but the inclination toward that thing.

Example: If we described someone as 'really loving tennis', their personality is not the act of playing tennis, but their love of playing tennis. Of course, those who love tennis to tend to play tennis, but there is a distinction there. It refers to a psychological attitude, and not the acts that flow from such an attitude. A person does not change their personality by being forced to do something.
However, the object of the inclination - what we are inclined to do or feel things about - is still central to understanding the inclination itself. So even though playing tennis and the love of playing tennis are different, 'the love of playing tennis' still contains the concept 'playing tennis', and thus the love can nevertheless not be understood without understanding what is loved.

However, we have an enormous amount of 'inclinations' - inclinations make up a large portion of our psyche. But not all of these are equally likely to be classed as someone's 'personality', and some wouldn't be at all.

Example: We love our family, friends, and lovers; we like and dislike foods; we enjoy and dislike certain hobbies; we desire or are averse to different things. But these things are not generally considered to be personality as much, because they are directed toward such specific things.
Example: We may feel like doing something one day, and feelings may come and go with time and situation. These are similarly not considered to be personality as much (even less than the previous), because they are so transient - they change or pass in and out of existence too much.
The first can be considered to be too specific in where the inclination is directed, and the second can be considered to be too specific in when or how long it is operating in our psyche.

So what kind of inclination would Personality be? Well, it would have to not be directed toward specific things, but have a more general applicability. Similarly, it would have to be something that persists across time, and is not therefore some specific action. Thus it cannot be found within any particular decision, but must permeate all of our decisions. What permeates all of our decisions? The decision making process itself.
What goes into all decisions? Well, as far as I see it, a brain or mind is a decision making machine. It's ultimately all about choosing what to do. Even when our thoughts do not relate directly to this purpose, I believe we possess the ability because it helps in decision making. Thus, other than the utterly unhelpful claim that the mind itself is involved in all decisions, what goes into all our decisions is the basic functions of mind - or in other words, the processes that underlie all activity of the mind, that make possible every thought, feeling we have.

After all, the human mind is controlled by Evolution. It is a decision making machine because that is why it evolved - to make decisions and thereby coordinate behaviour.

Evolution occurs not just by the process that kills off the unfit genes, but by the process that creates variation in those genes - this is why not all selection pressures help a species, and some just make them go extinct; some environmental pressures kill off or prevent reproduction faster than random genetic variation can occur to produce new, advantageous traits. Given that behaviour is crucial to the survival and reproduction of cognitive animals, personality variation may be how the human species 'tries out' different behavioural patterns to be selected for.
As social animals, humans are heavily reliant on the division of labour in one or another capacity; even if, say, all the men do hunting, they are more effective if they are doing different things (in coordination, of course). But life is more than just something like hunting - there are a wide range of different things we can do to improve our survival rate, and in different ways. Personality variation may be the way in which we are inclined toward different roles in our social group.

The 5 factor model (also known as Big Five or OCEAN) basically takes this attitude; it was created by asking people about how they and others fit a vast array of personality-related terms, and then seeing which ones correlated, and looked for the basic principles behind them. For instance, if they found that people who rated themselves or others as highly 'excitable' also rated themselves or others as highly 'social', they did not call 'excitable' or 'social' separate personality traits, but collapsed them into a single trait - in this case, Extroversion.
However Jung got there first (although others still before him). His system of Cognitive Functions, and perhaps more importantly the components of the cognitive functions, should be seen as a theory of the basic functions of mind, the processes that underlie everything that goes through our heads, and make our minds possible. It then describes personality as relative inclinations toward making use of a particular process or processes over others in general.

These functions being basic must therefore be simple, not (too) complex in themselves (although their interactions and combinations with each other and real life, giving rise to actual human thought, may end up being complex).
These functions being processes of mind means that they are how we think, not what we think. Another way of saying this is that they describe the manner of thought, and NOT the content of thought.
Finally, the fact that they are the basic functions of mind means that no one can lack any of them. As we said earlier, personality is the inclination toward or away from something, not what is inclined toward or away from. So the definition of an introvert is not necessarily someone who lacks the ability of extroversion, but someone who relatively prefers doing introversion over extroversion (although we do tend to practice what we prefer doing, and neglect what we don't).

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