Step 1: Context:
In 'The Rattrap' by Selma Lagerlöf, the peddler sees the whole world as a giant rattrap, with riches, joys, and comforts as tempting bait that ensnare people.
Step 2: Why he can be called a philosopher:
The peddler's rattrap analogy is a genuine, original philosophy of life — he observes that just as a rat is tempted into a trap by cheese, human beings are lured into traps of greed, comfort, and desire, only to lose their freedom. This is a profound, insightful way of understanding human nature and temptation, showing that despite his poverty and lack of formal education, he possessed genuine wisdom about life.
Final Answer:
He can be called a great philosopher because his simple rattrap metaphor captures a deep, universal truth about human temptation and the loss of freedom — genuine philosophical insight born from his own hard experience of life.