A number of points have been raised in this exchange that seem to call for   
further comment.  
  
  
  
1. Re Adam McHugh's second contribution;: I agree that. until recently many,   
probably most, economic theorists, and members of the general public, took   
technology for granted. (We have a long section in Chapter 1 of our book   
suggesting reasons for this neglect.)  The exceptions to are mainly found   
among economic historians, such as Mokyr and Landes, and general economists   
who have concerned themselves explicitly with technological change, such as   
Schumpeter, Nate Rosenberg and Chris Freeman.  
  
  
  
One interesting observation along the line of his interest in text book   
treatments is that few such books bother to define technology even when they   
discuss it. For example, in the Index to the 10th edition of my UK   
introductory text book (Lipsey and Crystal 2004) "technology" has 23 lines   
of references but NOT ONE for a definition. Neither does a definition appear   
in the 17 page glossary of terms! I now begin to wonder how many of those   
who have done major empirical and theoretical work on technology have   
bothered to define what they were studying. (Thanks for setting me a minor   
research task. I will explore this interesting question in the near future.)  
  
  
  
I agree with Mc Hugh that technology is implicitly defined in most texts in   
the way he states and that this definition probably stems from Hicks'   
treatment  in Value and Capital (although, of course, it may have earlier   
antecedents, and it is not the definition my colleagues and I use).  
  
  
  
2. To Robin Neill: I accept, and use, Marshall's terms "short run" and "long   
run" when doing comparative statics with technology constant. But my   
colleagues and I model continuous movement driven by endogenously generated   
technological change. For this reason, we are careful to use the term "long   
term growth" and never "long run growth".  
  
  
  
However, I disagree with Neill when he says  "Once these [technologies]   
change we are in economic history not economics." I agree that for a full   
understanding of the causes and consequences of technological change, we   
need to know a lot of history. But it is also possible to theorize about   
such changes in what is recognizably "economics". (For examples, see the   
models of endogenous growth by Romer and Lucas, the models of General   
Purpose Technologies (GPTs) in the book edited by Helpman, and the models in   
Chapters 14 and 15 of our new book,)  
  
  
  
3. To Donald Coffin: Yes, it is customary to follow Schumpeter in   
distinguishing invention, innovation and diffusion. But, contrary to his   
view, these are not related linearly, but in a system of mutual   
interdependence. For example, new technologies rarely, if ever, diffuse in   
unchanged form. As they move to new uses and to new places, they typically   
have to be altered to fit the local situation leading to further invention   
and innovation.  
  
  
  
4. To Prabhu Guptara and Sameul Bostaph, let me repeat the first line of our   
definition:  
  
"Technological knowledge, technology for short, is the set of ideas   
specifying all activities that create economic value."  Such knowledge gives the specifics
of the goods and services that can be made, how to make them, and how to organize their
production and distribution. In common with most theorists of the subject, we distinguish
between technological knowledge and the things in which that knowledge is embodied, such
as plant and equipment, infrastructure, firm location and organization. These are elements
of what we call the
"facilitating structure". Given new technological knowledge, no alteration   
in output and hence economic value is possible until that structure has been   
altered. Typically its various elements adjust with different time lags. The   
great advantage of making this split between technological knowledge and the   
artefacts that embody it and are used to create economic value is that it   
resolves the "Solow paradox". If one works with an aggregate production   
function with a form such as Y =Af(Labor, Physical Capital, Human Capital),   
changes in technology and changes in Total Factor Productivity (TFP) are   
identical; you cannot have one without the other. This gives rise to an   
apparent paradox when changes in one are observed without corresponding   
changes in the other. But given that new technological knowledge typically   
becomes embodied in the various elements of the facilitating structure with   
various lags, some of which can be decades long (as was the case when   
embodying the unit drive electric motor in factories and reorganizing those   
factories to fully realize the potential of this new type of machine), there   
is no paradox. For example, accelerating technological change can be   
combined with decelerating changes in TFP until the facilitating structure   
has been well adapted to the new technologies. Indeed, as well as arguing   
this verbally, this is what sometimes actually occurs in our mathematical   
models of endogenous, GPT-driven growth.  
  
  
  
5. Pat Gunning poses an interesting question as to how far one should go in   
defining technological knowledge to include knowledge that covers activities   
beyond the sphere of production (product, process, and organization). As   
Tony Brewer notes, the other activities mentioned by Gunning are important   
but are not usually included in studies of technology and technological   
change. Our definition includes knowledge of all of these activities. But   
definitions are our servants, not our masters and for some purposes the   
knowledge that contributes to these other activates might well be treated   
separately, rather than as one category of 'knowledge of how to create   
economic value' as we do. In practice, we spend most to our time on those   
activities that design and produce goods and services rather than those that   
distribute and sell them.  
  
Richard G. Lipsey