of the world on which ethics considerations are based. And now engineering also is putting pressure on science, philosophy and religion in terms of ethics.
In the broadest sense, engineering can be defined as an activity directed toward the modification of nature, from altering genes to the construction of bridges, from space flights to the fighting of disease—all processes or artifacts that did not exist in nature. This modification of nature is in effect a continuation of biology by other means, so that engineering—whether traditional engineering or genetic engineering or medicine—is a metabiological activity. Science, on the other hand, has the goal of understanding nature. The questions of science are why? and how? Those of engineering, in all of its thrusts, are how can we? Engineering achieves its goals through the design and operation of machines (artifacts), be they tangible, such as a bridge or the modification of a gene or a hip replacement, or intangible, such as a computer program or a therapeutic protocol. (I prefer the term ‘machine’ to artifact or device because in its Greek etymology—mechané—it also has a slightly pejorative connotation that fits our ambivalence about some impacts of technology.)
In the traditional sense of the word—used henceforth in this paper unless otherwise noted—engineering is a specific method for designing machines. There are complex interactions among engineering, the physical inanimate world, and the biological world that need to be identified as they are relevant to an understanding of where bioengineering and the ethical problems of bioengineering fit in the picture (Figure 1). Engineering, as an agent modifying nature, interacts with the physical inanimate world, and as an agent to extend biology, it interacts with the biological world. The specific interaction of engineering with the biological world thus far has been recognized primarily as the domain of bioengineering, although it is clear that all of engineering is centrally involved, whether it recognizes it or not, in the modification of the biological world (for example, a highway, by bisecting a habitat, changes the biology of that habitat). It is also clear that any significant engineering development has an impact on society, just as any significant societal development ultimately is likely to lead to engineering developments. We may want to note at this point that not only the artifacts—the machines—that are created by engineering, but also society are metabiological activities. Both machines and society extend biology by other means as they interact with biological organisms and with each other.
Traditionally, engineering has been focused on the outward extension of biological organisms, that is, on extensions that are external to the