I haven't even the material for guess-work.

Ought I to be able to arrive at any opinion on the subject ?" Thorndyke picked up one of the pieces, fingering it delicately and inspecting with a critical eye the flat base on which it stood, and reflected for a few moments.
"It is easy to trace a connection when one knows all the facts," he said at length, "but it seems to me that you have the materials from which to form a conjecture.

Perhaps I am wrong, but I think, when you have had more experience, you will find yourself able to work out a problem of this kind.

What is required is constructive imagination and a rigorous exactness in reasoning.

Now, you are a good reasoner, and you have recently shown me that you have the necessary imagination; you merely lack experience in the use of your faculties.