Mazal: getting the straight goods

What exactly is mazal? How does it work? Most importantly: what effect does it have on our lives and aspirations?

Let's search Talmudic literature for some clarity.

We must carefully distinguish between two very different forces - both called "mazal" in Torah sources. One is mazal as an independent representative or guide attached to or associated with every human being, and the other is a blind, purely mechanical and natural influence (sometimes associated with astrology). Later we'll explore the possibility of a third "mazal" force.

Personal Mazal

Despite the general prohibition against carrying objects in public places on Shabbos, the Gemara does permit certain protective amulets (קמיעות) to be worn as long as they have already been proven effective (מומחה). Nevertheless, even among those known to help people, they remain forbidden as long as they aren't proven effective on animals as well:

It would seem that the mere existence of this representative - which, by the way, does not seem to have any personal power - protects a person from damage even in circumstances that could kill an animal.

Similarly, a human being's personal mazal can protect him from violence as can be seen in Rashi's second approach to this Gemara:
Besides being somehow responsible for his safety, a man's mazal can also represent him in the spiritual world. As an example, the Gemara tells us that the Jews, once they stood at Mt. Sinai and received the Torah, were able to shed something called "zuhama". But what about those who converted to Judaism only later? How do we explain the absence of "zuhama" even among converts and their descendants?
This mazal-representative can also subtly link us to spiritual events and influences that we might otherwise entirely miss:
Mazal's protective strength is affected by a person's own spiritual level:
In other words, Rav Chiya bar Yosef's position is that the nature of mazal-influence can change - for better or for worse - according to a man's behavior and attitudes. It should be noted that Tosafos (Bava Basra 96b "ושמואל אמר") limits this effect to reasonably predictable phenomena, but maintains that a man's behavior cannot force his mazal to cause wholly miraculous changes in nature.

Mazal can be changed due to a person's physical circumstances. The Gemara relates a remarkable story about a messenger of the Angel of Death who accidentally "collected" the wrong woman. The angel was asked:
Even the level of a person's confidence can affect the strength of his mazal:
Mazal as a blind, mechanical force of nature (astrology)

While God may certainly intervene at will, Chazal seemed to observe natural forces that, if left alone, would produce predictable effects on human beings and their environment. The Gemara (Brachos 59a), for instance, notes that the flood only began when God removed two stars from one constellation and only ended when He took two different stars from another constellation to fill the gap in the first. The implication is that the continued influence of the original stars, had they not been moved, would have ensured stable conditions.

Whether this influence is absolute or whether people - or at least Jews - can somehow escape its effects, would seem to be a debate between Rabbi Chanina (and others including Rabbi Yehoshua ben Levi) and Rabbi Yochanan (along with a rather long list of like-minded sages including Rabbi Akiva) in the Gemara Shabbos (156a-156b).
The Gemara offers no obvious resolution to this debate. And even according to Rabbi Yochanan (who taught that the effects of mazal can be avoided), there are still limits to our self-determination:
The mazal of nature also seems bound to natural cycles (This would also seem to be as clear an indication as any other that "mazal" has no power or free choice of its own, but is purely unconscious and mechanical.):
And not only weekly cycles...
Additionally, Rabbi Yehoshua ben Levi associated the influence of mazal with the day of a man's birth while Rabbi Chanina considered his birth-hour more decisive (Shabbos 156a).

The Rambam

Against this background let's take a look at the Rambam:
The Rambam here possibly bases himself on passages in Chazal like Brachos 59a (which describes the stars' role in the onset and completion of the flood). He clearly identifies "guiding the world" as one of the stars' functions. However, we must be careful not to exaggerate his position.
Here's what he wrote near the end of the laws of idolatry:
In adding further context to the various prohibitions of the chapter, Rambam concludes:
So, while the Rambam does accept that stars do exert some influence on nature, he clearly rejects any connection between them and the conduct of human society. This distinction is made much more clearly in Rambam's letter to the rabbis of Marseilles in which, while debunking the authenticity of astrology, he outlines the position common to all "philosophers":

Rambam then writes that Torah belief differs with the philosophers only in that human events are not random, but are the result of Divine providence. They would all agree, however, that the stars have no influence on human life.

Now this most certainly seems to fly in the face of many of the quotations from Chazal we've referenced above. The Rambam was well aware of this problem and addressed it towards the end of his letter to Marseilles:
The Third "Mazal"

Rabbi Meir, in the final Mishna of mesechte Kiddushin, teaches that a person should make every reasonable effort to find success in a trade...
Tosafos (Kiddushin 82a), while commenting on the Mishna, wrote
But why, wondered the Tiferes Yisrael (echoing questions of the Tosafos Yom Tov), would Tosafos attribute wealth to mazal rather than merit (besides the fact that mazal and merit are quite distinct from each other): if mazal determines a man's financial fate, then why bother praying?

To this, the Tiferes Yisrael offers a creative solution. The term used by the Mishna (זכותו) doesn't actually mean "merit", but rather, its more common Talmudic translation: "possession" or "rights" (example: "<יש לו זכות בו"). In this case, the Mishna means to teach us that, besides prayer, our financial success or failure largely depends on the peculiar combination of circumstances into which God decreed each of us be born (that which can truly be said to be "ours"). After all, so much of a person's success does depend on his background and social standing. So, for instance, influences like one's inborn nature, family, environment, diet and education all play significant roles in his future chances at success.

This, of course, has nothing to do with any astrological influences (Tiferes Yisrael firmly follows the Rambam's approach), but is a direct result of God's specific plan for each human being. And, as did Tosafos, it is therefore quite reasonable to characterize it as mazal.

The Bottom Line

While it seems clear that our connection to the spiritual world is sometimes characterized by Chazal as "mazal", this knowledge would seem to have few, if any, practical applications - beyond the general need to care for our own physical safety and spiritual wellbeing.

It is certainly necessary to steadfastly avoid astrological advice - whether because Torah law forbids it or, according to Rambam, because common sense should guide us away from foolishness. Either way, in our search for financial success, there would seem to be very little room in Judaism for reliance on anything besides trust in God and hard work (in that order).

And we can take comfort in the knowledge that a great many of the crucial elements which will determine our success were given to us by our all-knowing and most-kind God.