But those who, perfect in their knowledge of God, turn their mind sometimes away from God, enjoy the presence of Divine Providence only when they meditate on God; when their thoughts are engaged in other matters, divine Providence departs from them...Hence it appears to me that it is only in times of such neglect that some of the ordinary evils befall a prophet or a perfect and pious man: and the intensity of the evil is proportional to the duration of those moments, or to the character of the things that thus occupy their mind... Hence it may occur that the perfect man is at times not happy, whilst no evil befalls those who are imperfect; in these cases what happens to them is due to chance (nature). This principle I find also expressed in the Law. Comp. "And I will hide my face from them, and they shall be devoured, and many evils and troubles shall befall them: so that they will say in that day, Are not these evils come upon us, because our God is not among us?" (Deut. xxxi. 17).The Rambam believes that a normal person does not experience divine providence for the majority of their lives. It is only an extremely righteous and knowledgeable individual that experiences divine providence. Therefore, most occurrences are not due to G-D's direct intervention, but through chance (nature). This approach leads the Rambam to take a much more proactive approach to medical care. Medical care is necessary, in fact obligatory, because G-D did not cause this illness. Chance (nature) is what causes most illness and that is why a Jew needs to take care of himself by staying healthy and going to the doctor. Also, this is why a doctor has an obligation to heal and not just permission.
The Rambam's obligation for a person to seek out a doctor can be inferred from his introduction to Mishna Avos (Ethics of Our Fathers, Chapter 3)
Likewise, just as when people, unacquainted with the science of medicine, realize that they are sick, and consult a physician, who tells them what they must do, forbidding them to partake of that which they imagine beneficial, and prescribing for them things which are unpleasant and bitter, in order that their bodies may become healthy, and that they may again choose the good and spurn the badRabbi H. Norman Strickman explains this excerpt to mean that the Rambam believes a person should consult a physician in times of illness. This idea is also seen in the Rambam's Mishna Torah (De'os 2:1, translation found here)
To those who are physically sick, the bitter tastes sweet and the sweet bitter. Some of the sick even desire and crave that which is not fit to eat, such as earth and charcoal, and hate healthful foods, such as bread and meat - all depending on how serious the sickness is. Similarly, those who are morally ill desire and love bad traits, hate the good path, and are lazy to follow it. Depending on how sick they are, they find it exceedingly burdensome...What is the remedy for the morally ill? They should go to the wise, for they are the healers of souls. They will heal them by teaching them how to acquire proper traits, until they return them to the good path.It seems like the Rambam believes that the remedy for someone who has bad character traits is the same as for someone who is sick, consult a wise healer. By the morally ill, the healer is someone who can help them with their lack in morality. For a physically ill person, the healer is a physician. This can best be illustrated later on in this section of the Mishna Torah (De'os 4:1 translation found here)
Since maintaining a healthy and sound body is among the ways of God - for one cannot understand or have any knowledge of the Creator, if he is ill - therefore, he must avoid that which harms the body and accustom himself to that which is healthful and helps the body become stronger.The Rambam clearly states that one must maintain a healthy body in order to properly serve G-D. He then goes on to list advice, as a physician, as to how people should maintain their health. So, it appears to be that the Rambam believes that there is an obligation, if not a necessity, for an ill person to consult a physician. (This allows us to contrast the Rambam with Ramban. The Ramban believes a person SHOULD NOT consult a physician as seen here.)
The Rambam's obligation for a Jewish Physician to heal is, actually, somewhat innovative. As pointed out by Benjamin Gesundheit (In Rambam Maimonides Medical Journal),
Maimonides did not accept this well known apologetic attitude of the Talmud towards medicine based on his philosophy of life (Weltanschauung), and he was the first Rabbinic author to understand medicine as a fundamental and a-priori religious duty anchored in a well known Biblical source and further supported by its Talmudic interpretation.The reason for the Rambam's innovation is, as Gesundheit says, because of his philosophy of life. This also led him to a very interesting source for a physician's obligation to heal. Most commentators bring the verse from Shemos (21:19), "And he shall surely be healed." This is talked about in the Gemara (Babba Kama 85a)
The School of R. Ishmael taught: [The words] "And to heal he shall heal’’[is the source] whence it can be derived that authorization was granted [by God] to the medical man to heal.However, this verse only creates permission for a physician to heal. Therefore, many commentators conclude that a physician has no obligation, only permission. That is why the Rambam learned a physician's obligation to heal from a completely different verse. This is seen in the Rambam's commentary on the Mishna (Nedarim 4:4),
There is a Biblical obligation for the physician to heal a sick Jew. This is included in what is explained about the verse (Devarim 22:2) "And you shall return it to him." [This includes] healing his body, for this is like when you see him in danger and you are able to save him with your body, your money, or your knowledge.Ingeniously, the Rambam takes the obligation to return a lost object to mean anything that is "lost" must be returned. In this case, if a person has "lost" his health and a physician has the ability to "return" it to him, then the physician is obligated to do so. (See also Mishna Torah Hilchos Nedarim 6:8)
Rambam's unique source that leads to the physician's obligation to heal also leads to another innovation. A Jewish physician is obligated to heal even a sick non-Jew in a case where it will create a sanctification of G-D's name, a desecration of G-D's name if he does not, or simply because it is "the way of peace" (Laws of Theft and Lost Objects 11:3). We also see that the Rambam "practiced what he preached" from his letter to Rabbi Samuel Ibn Tibbon (found in Freidlander introduction to The Guide),
I reside in Egypt (or Fostat); the king resides in Cairo, which lies about two Sabbath-day journeys from the first-named place. My duties to the king are very heavy. I am obliged to visit him every day, early in the morning; and when he or any of his children or the inmates of his harem are indisposed, I dare not quit Cairo, but must stay during the greater part of the day in the palace. It also frequently happens that one or two of the royal officers fall sick, and then I have to attend them. As a rule, I go to Cairo very early in the day, and even if nothing unusual happens I do not return before the afternoon, when I am almost dying with hunger; but I find the antechambers filled with Jews and Gentiles, with nobles and common people, awaiting my return.It appears that the Rambam believed treating non-Jews was just as important, in most situations, as treating Jews.
In conclusion, we see the approach of the most rationalistic Rabbi, Rambam (Maimonides). My personal belief (in congruence with the belief of other, more knowledgeable people) is that his approach to the medical profession stems from his philosophical outlook on life. He believes that G-D does not cause most illnesses directly, therefore, he believes that if man has the capabilities to cure those illnesses, he should. This is why, I think, he finds the acts of preventing one's own illness, seeking out a physician, and a physician healing not to just be permissible acts, but obligations. Many Rabbis before and after the Rambam would not even say it is permissible to seek out a physician and they barely even allow a physician to heal. In response to these Rabbis the Rambam would say, "But the Gemara is CLEAR!!! Return it to him, return his lost health. It's a Mitzva (commandment)!"