This paper aims to diagnose the epistemological thinking of a wide sample of in-service teachers by means of the Questionnaire of Opinions on Science, Technology and Society applying a new powerful quantitative methodology that allows inferential statistics (significance tests of differences). The analysis compares science and art teachers thinking, a rare agenda in science education literature as it is usually focused in science teachers. The results show neutral, slightly positive global attitudes, and the detailed analysis allows identifying the teachers' most positive and most negative beliefs. The comparison among science and arts teachers indicate that overall science and art teachers do not differentiate at all, contradicting one would expect; besides, science teachers' attitudes are slightly worst than those of the arts teachers. The implications of these results for the teaching of nature of the science and technology contents and for the training of science teachers are discussed.