We must try before we die! — Agent Smith
Yes, Suicide is the last thing I do. But depression being caused by serotonin deficiency overlooks, in my optimist opinion, the cause for the deficiency, which in a broader context can be seen as an effect of depressing causes. Somehow, the view that neurotransmitter shortage is the cause has it backwards. Depressing circumstances can do the trick.
-Woman
A Sum of infinite complex vectors, with time-variable lengths and rotating with time dependent angular velocities, similar to, but not to be confused with Fourier series:
Depression:
The minimum of the
God Function, of which sights have been reported. Its exact shape remains largely unknown. Progress is being made though, and probably within the current decade the problem is solved. Breakthroughs have recently been achieved.
Religion:
The God Function
Atheism:
The Hermitian conjugate of the God Function. Though it has been conjectured It's the inverse. Depends on the God Function. Extremist atheists consider the minus symbol sufficient.
Pessimism:
The constant function
Cause:
This one is kind of tricky. There are lots of thoughts about cause and effect. Let's take the physical approach. A force causing an irreversible increase in entropy. Which means every process. Even the seemingly reversible process of two particles interacting by a coupling to a mediating virtual field. Force is the causing factor while initial conditions determine if time goes forwards or backwards. If cause precedes effect or effect cause. Cause cannot exist without effect. So let's define cause as the generator of the effect, separated in time. The most general cause is a non-local one. The particular local cause being a limit of the non-local cause. How can we define the generator of cause? How does matter forces, causes, other matter to change velocity? By coupling to the intermediary virtual condensate, omnipresent in space. How does matter couple to it? By means of charge. Electric charge couples to the virtual photon field. The virtual fields couple, again because of charge, couple to other virtual fields, giving rise to higher order interaction. For example, the virtual photon field couples to the virtual electron field only, which again can couple to the virtual photon field, which again can couple to the virtual electron field, etc. The changes in momentum of two charged particles is caused by all this virtual mediating. The Feynman diagrams represent all this virtual intermediary happenings. A first order diagram by coupling to a virtual intermediary photon (in popular prose referred to as a photon exchanged, which is a rather inaccurate description, as is the short appearance of particle/antiparticle pairs which is actually just one particle rotating). Second order diagrams by permitting the virtual photon to interact with a virtual electron (closed loop) or including an extra virtual photon. Third order by permitting an extra virtual electron again or permitting the previously added virtual electron to couple to a virtual photon. Etcetera, etcetera. This procedure is supposed to go on and on, giving rise to divergent integrals, which are solved by renormalizing. The supposed(!) point-like nature of fundamental matter is the root of the problem. Circumvent this problem (as is only partially done in string theory), and no renormalization needs to be done (Dirac called it a stop gap procedure and Feynman thought it a magic joke).
So, how can we describe a cause with math? Good question! I'll leave the answer to fellow philosophers. What has to be included? Force or interaction. Time running in one direction. Which could be backwards but then the effect precedes the cause, i.e., the effect becomes the cause, while the cause becomes the effect. There should be charges included. And mass. Velocity. Is gravity actually a causing force? Good question. Shall we make an effort?