In chapter 3 of his "Discourse on the Method" (titled: "Morals and Maxims accepted while conducting the Method") René Descartes is getting to ready to dive into the rabbit hole of methodological doubt. Before he does that he makes sure to inscribe for himself a few methodological precautions to complete the rules described in part 2 of the book.
The first rule of chapter 3 is to remain obedient to the law of his country and religion. It's not that Descartes believes that these laws are necessarily true, but his thinks that should he lose everything he knows, these will at least serve as good guidelines to fall back on. Descartes also resolves to follow the actions of those in his country that seam most sensible, for much the same reasons.
The second rule Descartes devises for himself is decisiveness of action. Taking a wrong path is better than no path at all, and making a wrong decision is better that no decision since that latter would keep us in our place. In a sense what Descartes is saying is that over thinking can be stagnating.
The third rule Descartes proposes in chapter 3 of "Discourse of Method" might sound a bit New-Age, arguing that his intent is not the change the world (on which he has no influence) but rather to change himself and the manner in which he perceives his world (something which in entirely up to him). This is not only modesty on Descartes' part but also a will for autonomy and a desire not to be conditioned by external factors. The one thing we have control over in this world is our thoughts, and we should make sure that it stays that way.
These maxims are not suggested by Descartes as a moral code, but rather as a way of optimizing his method in search of certainty. Part 4 of "Discourse on the Method" will find to such certainties: God and the Soul.
See additional summaries on Descartes' "Discourse on the Method":
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