There is nothing to suggest that he has studied to any great extent Van Til's 'presuppositional' philosophy. He cites Van Til's book on common grace with no reference to its bearing on the imperative of presuppositional analysis. He also quotes from Alvin Plantinga, but no hint of learning about a presuppositional way of thinking is indicated. Thiessen identifies the use of presuppositional thinking among contemporary thinkers as a given. Wherever it comes from, we can be thankful that this kind of thinking is gaining some importance among philosophers.
Science is the paradigm for teaching according to the contemporary ideal of liberal education.
Thiessen shows that there is as much or more bias in the content and methods of teaching science as there is in religious instruction. In fact, he argues that Christian instruction that follows the dictates of the Bible is far less oppressive than the content and method that marks the teaching of science in the public schools. If one grants the legitimacy of the Enlightenment ideal of liberal education, then the evidence shows that Christian training receives a higher mark for being humane. Thiessen ably argues that the humanist ideal of a liberal education is not defensible as a theory that has some meaningful tie with reality. His reconstructed concept fits the requirements of both public education and Christian schools.