The dis­tinc­ti­ve fea­ture of modern sci­ence as an acti­vi­ty rather than as a body of know­ledge is expe­ri­men­tal mode­ling. Through expe­ri­men­ta­ti­on modern sci­ence con­structs models of dif­fe­rent natu­ral pro­ces­ses, and by means of argu­ments based an a princip­le of pro­por­tio­na­li­ty uses them to rea­son from known or obser­ved cau­se-effect rela­ti­ons­hips to unknown cau­ses of known effects. Gali­leo Gali­lei (1564—1642) was the pioneer of such mode­ling in phy­sics (fal­ling bodies), which has sin­ce been exten­ded to che­mi­stry (ato­mic models), bio­lo­gy (models of DNA), and even human psy­cho­lo­gy (com­pu­ter mode­ling of cogni­ti­ve proees­ses).[7]

Modern sci­en­ti­fic expe­ri­men­ta­ti­on con­structs models of what (it thinks) alrea­dy exists, to expand knowing. The acti­vi­ty of design con­structs models of what (it thinks) might be, to extend making. For sci­ence, models take in or recei­ve and sim­pli­fy com­plex phe­no­me­na, ther­eby dis­clo­sing order. For modern tech­no­lo­gy, or sci­en­ti­fi­cal­ly refi­ned making and using in all their diver­si­ty, models pro­ject com­plex pos­si­bi­li­ties in rea­listic form, thus deter­mi­ning or enab­ling the con­trol of power. When this pro­jec­ti­ve mode­ling exhi­bits a con­cep­tu­al break with the final result toward which it is poin­ted, a break to be brid­ged by ana­lo­gy, it takes on its dis­tinct­ly modern character.

Design models in engi­nee­ring can, for instance, be “true” models, alt­hough more com­mon­ly they are merely “ade­qua­te” or even “dis­tor­ted” and “dis­si­mi­lar.” As one engi­neer has put it, “A dis­tor­ted model is [one] in which some design con­di­ti­on is vio­la­ted suf­fi­ci­ent­ly to requi­re cor­rec­tion of the pre­dic­tion equa­ti­on. Under cer­tain con­di­ti­ons, par­ti­cu­lar­ly whe­re flow of flu­ids is invol­ved, it is imp­rac­ti­ca­ble, if not impos­si­ble, to satisfy all of the design con­di­ti­ons [under a com­mon sca­le].”[8] Like­wi­se, “dis­si­mi­lar models are models which bear no appa­rent resem­blan­ce to the pro­to­ty­pe but which, through sui­ta­ble ana­lo­gies, give accu­ra­te pre­dic­tions of the beha­vi­or of the pro­to­ty­pe.”[9] (This should pro­bab­ly be “suf­fi­ci­ent­ly accu­ra­te.”) Ano­t­her engi­neer dis­tin­guis­hes bet­ween models that are “total­ly direct,” “total­ly indi­rect,” “com­bi­na­ti­on,” “visu­al,” and “com­pe­ti­ti­ve” with each being sui­ted to test dif­fe­rent aspects of a new idea.[10] All such models can be mani­fest in drawings, block dia­grams, net­work sche­ma­tics, mathe­ma­tics, phy­si­cal mate­ri­als, and rela­ted sys­tems of representation.[11 . See Mid­den­dort, Wil­liam H. (1986), Design of Devices and Sys­tems. New York: Dek­ker, pp. 156 ff. (Note, in pas­sing, that the posi­ti­ve con­no­ta­ti­ons of “sche­ma­tic repre­sen­ta­ti­on” build on while trans­forming the tra­di­tio­nal nega­ti­ve impli­ca­ti­ons of a “sche­me.”)]

Recep­ti­ve, sci­en­ti­fic mode­ling embo­dies know­ledge; with regard to know­ledge, embo­di­ment necessa­ri­ly ent­ails sim­pli­fy­ing con­cepts. Pro­jec­ti­ve, tech­no­lo­gi­cal mode­ling dis­em­bo­dies action; with regard to action, dis­em­bo­di­ment that lea­ves things out, idea­li­zes them. The for­mer mate­ria­li­zes, the lat­ter dema­te­ria­li­zes. The para­do­xi­cal aim of pro­jec­ti­ve, dema­te­ria­li­zed or idea­li­zed mode­ling is not so much explana­ti­on as prac­ti­cal leverage or effec­ti­ve­ness. The pre­sent and its desi­res are cast with gre­at for­ce and power into the future. Becau­se of the com­ple­xi­ty of varia­bles, theo­ry alo­ne can­not be used to dedu­ce, for instance, the shape of an air­foil, or to deter­mi­ne the Opti­mum spa­ti­al arran­ge­ments of ele­ments wit­hin a given struc­tu­re. Engi­neers have to “figu­re out” such things by simu­la­ti­on, often employ­ing a varie­ty of models. So they con­struct a minia­tu­re, model air­foil and test it in a wind tun­nel (now in a com­pu­ter pro­gram); by means of such acti­vi­ties they are tes­ting not some illus­tra­ted theo­ry but a repre­sen­ted arti­fact.[12] For struc­tures, engi­neers crea­te sca­led-down floor plans or two-dimen­sio­nal faca­des in order to play with alter­na­ti­ve arran­ge­ments of shapes by means of sket­ched geo­me­tries or mani­pu­la­ted cutouts. In each case the model or mock-up con­sti­tu­tes a tem­pora­ry reduc­tion to be even­tual­ly sca­led up in the pro­duc­tion not of know­ledge but of objects. Design uses crea­ted micros­ca­le cau­se-effect rela­ti­ons ren­de­red in models to engi­neer known or crea­t­a­ble macros­ca­le cau­ses into the pro­duc­tion of desi­ra­ble or desi­red macros­ca­le effects.[13]