(what is the purpose of this structure?)
In which I prove from evidence that G-d exists and outline my immature ethical theory...
First, let's define G-d for the purpose of this proof as a conscious, willful, purposeful creator of all existence. (I am not saying that that's all that G-d is; I am saying that this is one of His roles/behaviors.) Furthermore, let's assume that all creation is constant, i.e., that G-d is a continuous creator (I will show below why that's important).
I am not completely sure this proof is correct, but I am writing it out just in case.
The outline of the proof is as following:
1. Without G-d, objective morals cannot exist.
2. But morals do exist, per our observation, and they are necessarily objective.
3. Therefore, G-d must exist.
By the way, the part of the proof that most people (including campus Chabad rabbis) oftentimes miss is number 2. Without that part, one can just answer to number 1: "ein hachi nami" ("So what? I agree with you...") and move on without having to accept number 3.
Now the proof itself:
1. Without G-d, objective morals cannot exist.
Evidence for this statement can be presented in multiple forms. For one of them, you can watch this debate video (assuming you agree with the second speaker and not the first):
But here is my own idea of why you cannot have objective morality "simply 'cause": it doesn't make sense.
Ought statements are prescriptive. They prescribe that something should be done for some purpose. For instance, imagine that someone asks you where you should stick needles into a human body. Well, if his purpose is to torture the person, then you might give one kind of answer; if his purpose is to do acupuncture then you may give another answer (assuming you're an expert at both). But saying that morality is a description of what you must do, "just 'cause", without any particular goal (it's just the right thing to do, but for no actual reason) is nonsensical. It's not saying anything.
One might say that the purpose of moral ought statements is to do good. One ought to do those things that are good and ought not to do things that are bad.
My problem with this definition is that it's circular. We do not have a good definition of what good and bad are outside of prescription. Good and bad are descriptions of certain things that we ought to either gravitate to or stay away from. That is how we define good and bad subjectively anyway. We say that in our opinion (according to our tastes) a movie is good in the sense that it would be "oughtful" to go see it, for whatever purpose (to enjoy oneself, to derive some lesson from it, etc.) — but we see that the purpose must be included in the definition of "good" (movie or anything else); otherwise, it makes no sense to use that concept (as above with the needles).
Well, this is subjective good (a Quentin Tarantino movie may be good for me, for the purpose of enjoyment, but not for my wife who hates violent movies). On the other hand when we say that morals are objective, we mean that objects and events independent of our mind have quality of goodness (or badness) to them. But, as I hope I have shown, the concepts of goodness and badness must include a purpose to them!
But how can there be an absolute, "objective" purpose to the world out there? I walk in a forest and see a beehive. My purpose for it is to eat the honey to satisfy my hunger. The bees' purpose is to keep the honey to feed their larvae. Maybe somebody else's purpose is to take the honey and sell it on the market. How can there be an "ultimate" or absolute purpose, independent of any agents, built-in into the fabric of reality of the beehive? Clearly there cannot be, unless there is one agent who imbues all reality with a purpose: that who created and continues to create the beehive, consciously, willfully, and with a certain goal in mind (so to speak). I.e., G-d (per our definition above).
2. Morals do exist, and they are necessarily objective.
I am not going to provide a full proof for this statement here. Instead, I want to direct my reader to an essay by a philosopher Michael Huemer: "Moral Objectivism" (not to be confused with Ayn Rand's philosophy under the same name). I also encourage you to look at some of his other essays (and an excerpt from one of his books) in the Ethics and Metaethics section of his website.
Dr. Huemer basically argues in favor of the position that things can be good and bad in and of themselves, just like they can be red or green (or two or three in number) in and of themselves, independent of the observer. Please refer to the linked essay for the detailed analysis.
Note that Dr. Huemer is not arguing that objective goodness or badness of things is independent of any source (such as G-d); he is arguing that from our experience of dealing with goodness and badness and intuiting those qualities about events and objects, we must conclude that they are objective and not merely "figments" of our minds (like our tastes or emotions are). Hitler was evil in and of himself, independent of anybody perceiving him as such and not in definition of the targets of his evil acts. I.e., that Hitler killed a lot of Jews was certainly bad for them, but we also think that the fact that he caused all that harm was an evil event in itself, not just from his victims' point of view (and not just because we fear that he or someone else might do the same to us, chv"sh).
(Otherwise, it would be nonsensical to argue that murder is wrong: after all, if it's only wrong subjectively, from the point of view of the victim, then the victim is no longer there! So, once the victim is dead, the murder is no longer wrong, as there is nobody anymore to whom it could be wrong. But a murder is by definition murder only after the victim has been killed.
The best one could say then is that it's wrong because it caused suffering to the victim's family, but that is not what we mean when we say that the act of murder is wrong independently of whatever side effects it caused. I.e., yes, murder is wrong because it causes suffering to the living, but first and foremost it is wrong because it eliminates life — even of a completely useless person who has no relatives or friends. Likewise, we must distinguish between wrongness of murder and that of threat of murder.)
Again, see the essay for more details. He addresses possible objections like: "Well, maybe we are just being empathetic to the victims and that results in a psychological feeling of 'evil' in our mind."
3. But if all the events and objects can be objectively good and evil (shown in 2), but cannot be understood or defined as such without subscribing to them some purpose by an absolute purpose-giver (shown in 1), there must be such an absolute purpose-giver: namely, a continuous, willfull, conscious, and purposeful Creator of all reality. (The Creator must be continuously creating all the reality for us to say that it has a constant purpose.)
Quod erat demonstrandum.
One might point out that the above does not explain why we ought to carry out G-d's purpose for creation. I.e., why G-d's purpose is binding on us. (A wrong answer in my opinion is to say that we must do so out of duty to G-d or because the world is His property. Such answers presuppose that duty or respect for property are moral concepts worthy of consideration, but we are trying to derive objective morality from G-d's purpose for the world, not vice versa.)
My answer is that the above simply defines "objective good" as G-d's purpose for the world and explains why it must be so. It doesn't motivate one to actually do objective good.
First of all, it seems that it's better to have some definition of objective good than no definition at all, or to say that it is just a quality that we perceive in the world. We could say that about "red color": there is no way to explain what it is besides saying that it's just something we perceive as true — aye, that's not the case because now we know that color corresponds tp a wavelength of visible light, but we might have said that before we knew the nature of color (i.e., I sense this thing called color, and there is nothing else I can say about it, just that there is a modality of my consciousness caused by a phenomenon called color out there in the world). But we can't possibly say that about good because, as I explained, goodness is by definition prescriptive: it is that to which we sense a need to gravitate to.
Second, we might say that our intuitive feeling of goodness is one the good's principia cognoscendi (its giluim): the qualities by which it can be recognized (the other being the fact that G-d told us that he wants it to be done). On the other hand, the fact that good is G-d's purpose for the reality is good's principium essendi (its atzmus): the description of what it is. One can still identify good or bad through his intuition, not only through Halacha; I am just explaining what it is that he is identifying. (Likewise a physicist might explain that when I feel cold, I am sensing indirectly the average kinetic energy of molecules around me.)
Third, one could give a number of subjective selfish or aesthetic answers (one wants to be one with G-d; one wants to deserve Heavenly rewards; one simply wants that G-d's purpose be done out of love to G-d). In that case, objective morality derives from one particular case of subjective desires. I am fine with that in this particular case.