How does the Supreme Court find in the Constitution what is not in it?

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This has always been a mystery to me.

Let’s take abortion as an example

The word “abortion” does not exist in the text of the Constitution. The framers of the Constitution worried about slavery, not about abortion. Abortion became an important issue in the twentieth century. Now in Roe v Wade the Supreme Court decided that abortion was constitutional. But today it is about to reverse itself. Is the Supreme Court like a weathervane that is guided by the…