I will start by giving a very simplified functional subdivision of the human Central Nervous System. Based on function, human brain can be divided into three areas
1. Brain stem: Brain stem is an upward continuation of spine. It is concerned with functions like controlling heart rate, regulation of blood pressure, breathing and some digestive functions to name just a few. Some of these are vital functions so an injury to brainstem could mean immediate death. That is why special care is taken to stabilize the neck in road traffic accidents.
2. Limbic System: This is a group of structures in our brain which together are involved in controlling behavior and emotions- Anger, pleasure, fear and punishment, reward, rage, curiosity, hunger, satiety, sexual drive, motivation and passivity. All of these come from the limbic system.
3. Cerebral Cortex: This is what we call the higher brain in laymen terms. It performs the ‘executive functions’. The prefrontal cortex(PFC) occupies the anterior portion of the frontal lobes and is thought to be one of the most complex anatomical and functional structures of the mammalian brain.
- All living creatures have some system for maintain vital body functions like breathing in place of brainstem.
- All vertebrates possess a limbic system so dogs, cats and other animals are able to feel and express emotions.
- Amongst vertebrates the only classes to possess the characteristic cerebral cortex are mammals (and some reptiles, lolz, so the conspiracy theories about the world being controlled by an elite group of reptiles could turn out to be true)
- Amongst the mammals Allah (سُبْحَانَهُ وَ تَعَالَى) bestowed the humans with the most highly developed cerebral cortex of all its creations on earth. When I say highly developed I don’t mean size or surface area relative to body, I mean functionally development and intellectual capabilities. Humans are probably intellectually highest of all the earthly species created by Allah.
It is because of this highly developed cortex that humans sit at the top of the hierarchy and have been called ‘Vicegerents of Allah’ on earth. Of course, not any two footed being in human form can be the vicegerent of Allah(سُبْحَانَهُ وَ تَعَالَى). He also has to manifest divine attributes in both his private and social life.
So our cerebral cortex is capable of ‘higher mental functions’ like thinking, abstraction, planning, decision making and controlling the limbic system! This last function is probably its most important function.
The brainstem functions are not under our conscious control. Obviously we cannot tell our bodies increase or decrease the heart rate or blood pressure. Higher mental functions are almost always voluntary.
The limbic system sits on the the borderline between brain stem and cerebral cortex both structurally and functionally (the word limbic means borderline in latin) What does this mean? This means that we can choose to exercise control over our behavior and emotions using the executive powers of cerebral cortex or we can let the limbic system run loose and let it do whatever it wants in which case a human would be expressing a range of unbridled emotions anger, curiosity, sexual drive etc
Let’s look at some differences in capabilities of humans vs animals which are manifested by virtue of an intellectual cortex and are important from a religious perspective.
- Animals are incapable of learning about haram and halal. That’s why Allah(سُبْحَانَهُ وَ تَعَالَى) didn’t make it obligatory on them to respect these boundaries. It is the cerebral cortex and its associated areas which give the humans the capability learn this and differentiate between the two in various life situations. But if the humans choose not to utilize the cerebral cortex for this purpose and let their limbic system(emotions) take over, they lose the differentiation and in those instances they are acting like animals. This can easily be observed in the most primal of behaviours like consuming food and copulating and also in advanced actions like earning rizq through unlawful means.
- Animals cannot be taught moral and ethics. If your pet dog steals a piece of meat you can arouse feelings of fear and punishment in it but you cannot teach him why stealing is wrong. This is again due to the absence of the cerebral cortex that humans possess and probably this is the reason why animals won’t get punished for misconducts in the akhirah like humans.
- Animals cannot differentiate between tahara and nijasat. Again this is something which is a function of cerebral cortex. Physical purity is something which is very crucial in Islamic faith.
- The principles of mahram/namehram can only be comprehended by humans.
Looking at the above we can see how intellect elevates humans from the level of animals to vicegerents of Allah. Maybe this is why most of things that are counted as sins in islam are in principle limbic system(emotions) overriding the cortex(intellect)
- Anger- limbic system taking charge,
- Zina and haram lust – limbic system taking over humans,
- Consuming haram food and even stuffing yourself with halal food- limbic system satiety centre gone out of control,
- Curiosity- Even though the mechanism behind curiosity isn’t very well understood because it is difficult to differentiate curiosity from information seeking but what research has discovered so far is that a part of the limbic cortex is involved in both regulation and reward that is associated with curiosity(1). In Surah Hujraat (49:12) Allah forbids us from spying and ‘Tajassus’ but if limbic system is not controlled the person could be snooping around other people’s affairs, just like an animal would sniffs and examines any object in vicinity.
- Gambling – During gambling intellectual areas of the brain like prefrontal cortex show less activity than limbic areas depicting a link between gambling and limbic system(2) What’s interesting is that in an animal study conducted on gambling ,some species of animal demonstrated the same choices and psychological behavior as pathological gamblers. So, when Allah(سُبْحَانَهُ وَ تَعَالَى) made gambling haram it was probably to not let humans reduce themselves to animals.
- Drinking –Alcohol impairs functioning on the prefrontal cortex, disrupts normal pattern of neuronal activity required for decision making and thinking and hence leads to limbic system taking over. This is manifested a as lack of inhibition in people commonly observed in people who has ingested alcohol.(3)
If we look at Jihad bil nafs in medical terms it’s just a battle between limbic system and cerebral cortex.
Looking at the lives of Ahlulbayt (عليه السلام) we won’t find any instance where we see limbic system ruling over them. There is a famous incident where in the battle of Khandaq, where Imam Ali(عليه السلام) was on Amr bin abde Wud’s chest and about to kill him but then he abused Imam Ali(عليه السلام). At this Imam Ali (عليه السلام) moved from Amr’s chest and walked away. After the battle was over people asked Imam Ali(عليه السلام) the reason why he had spared Amr’s life when he had first overpowered him. At this he replied,” When I had floored him, he abused me, as a result of which I was overcome by rage. I feared that if I were to kill him in that state of anger, it would be for pacifying my anger. So I stepped away from him till my fury subsided when I returned to sever his head from his body only for the happiness of Allah and in obedience to Him.” (Manaqib Al Abi Talib by Ibn Shahrashub)
In Sahifa e Sajjadiya, Imam Sajjad (عليه السلام) has described three types of worshippers
i. Those who worship Allah because of fear of hell
ii. Those who worship Allah to get to Jannah
iii. Those who worship Allah because they find Allah worthy of worship.
He(عليه السلام) says the third is the highest form of worship. Why? Because the first two are worship of punishment and reward (limbic system worships) while the third is the worship of intellect (Prefrontal cortex).
So if we learn to control our limbic systems through reflection and worship gradually, we gain power over our nafs and then no amount of worldly temptation and desires can then take us away from out true purpose, that is submission to Allah(سُبْحَانَهُ وَ تَعَالَى).