The inductor is a magnetic circuit element. As long as the magnetic flux linkage created by the inductor current does not saturate, we can comfortably use the inductor’s terminal relations in circuit operation. The complication arises when we let the magnetic flux saturate under the influence of magnetizing force. So what? Why should one be concerned about cores that saturate? You do not need to worry about them in the twenty-first century, but they did bother our fellow engineers in the twentieth century.