There seems to be a general penchant for dichotomous styles of thought in engineering, in which hierarchies and gender are often evident - both symbolically and organizationally. This paper explores these themes, drawing in part on a pilot ethnographic study of software developers. The technical/social distinction is strongly gendered inasmuch as it maps on to masculine instrumentalism and feminine expressiveness. Also, the two sides of this dualism are seen as mutually exclusive such that 'the technical', which defines the core of engineering expertise and identity, specifically excludes 'the social'. Still, the related distinction between specialist and heterogeneous roles becomes valued, and gendered, in contradictory ways. The abstract/concrete dualism is even more contradictory. The privileging of analytical abstraction in science and education sits sometimes uncomfortably alongside the obvious practical importance of, and pleasures in, a hands-on relationship with technological artefacts - conflicting versions of masculinity. Multiple tensions coexist around such dualisms, yet they endure. The concluding discussion considers possible factors related to the co-existence of certainty and uncertainty around technology, and to the performance of gender more generally.