Reversability of the 40 Principles of Problem Solving

Todd Williams
3M Corporation, St. Paul, MN

Ellen Domb
The TRIZ Institute, 190 N. Mountain Ave., Upland, CA 91786 USA
+1(909)949-0857 FAX +1(909)949-2968

The 40 Principles of problem solving are among the oldest tools of TRIZ, and are used by most students of TRIZ when they first learn the basic TRIZ problem solving methods. (For a downloadable list of the 40 principles, with examples, see the article "Contradictions" in the July, 1997 issue of The TRIZ Journal.) They are included in all the commercial TRIZ-related software, and in the popular books available in English. (References 1,2,3,4,5,6)

The principles were developed during the initial patent research by H. Altshuller and his research colleagues, and provide methods, with examples, for solving large classes of inventive problems. The 40 principles themselves display both symmetry and asymmetry; that is, some of them are reversible (Principle 1, segmentation, and Principle 5, merging) and some are not (Principle 40, Use composite materials.)

The table below is a listing of the 40 principles, the opposite to each principle if one is obvious, and some examples of the opposite. We invite readers of this journal to contribute their own suggestions for completing the table. We have found that this is a useful exercise for classes in which people are learning the 40 principles for the first time.

We have speculated that the asymmetry of the 40 principles arose because these are principles for solving INVENTIVE problems, and the opposites may be the solutions for ordinary problems. (For example, use homogeneous materials is the opposite of use composite materials, but is not an inventive solution. Substitute fields for mechanical means is inventive, use mechanical means only is not, etc. ) We invite readers who participated in the research to write and let us know the history of the asymmetry of the 40 Principles. Please send you comments to

# Principle Opposite Examples
1 segmentation merging (#5), integration, agglomeration integrate functions on a chip; fax, printer, copier in one device
2 taking out merging (#5); adding in  
3 local quality universality (#6); global quality  
4 asymmetry symmetry; balance two blade paddle; lever going to seesaw; symmetrize laser beam to get better focus for cutting
5 merging segmentation (#1); separating  
6 universality local quality (#3); locality  
7 nested doll mutual exclusivity or mismatch asymmetric telescoping shaft so it can be locked in place; incompatible shapes to help sorting or avoid mix-ups - like electrical plugs for different voltages
8 anti-weight weight add weight at one end of buoy to keep upright (also asymmetry); keel on sailboat; weighted bowling ball rotates for curve; heavier golf club head; heavier ax head, fishing sinker or lure
9 preliminary anti-action preliminary action (#10); afterward anti-action design polymer to biodegrade; design products for recycling
10 preliminary action preliminary anti-action (#9); afterward action delayed catalyst cure of resin; moisture or light cure; reusable shipping package; recyclable toner cartridge
11 beforehand cushioning afterward cushioning built-in indicator for failure
12 equipotentiality increase potentiality gravity feed conveyors in plant; electrophoresis
13 the other way round internally contains opposites  
14 spheroidality - curvature linearity put flat on bottom of blown bottles; make TV screens flat to improve image; convert turning motion of motor into linear conveyor motion
15 dynamics statics crash-worthy passenger compartment in auto; industry standard devices: plugs, bulbs; hose threads; magnetostrictive fluids
16 partial or excessive actions this is its own opposite  
17 another dimension increase or decrease dimensionality make a one-story rambler instead of two-story Victorian house; make flat Fresnel lens
18 mechanical vibration remove vibration air-bearing table for optics lab; vibration isolation dampers for buildings
19 periodic action periodic inaction; continuous action (#20)  
20 continuity of useful action periodic action (#19); continuity of useful inaction  
21 skipping do at low speed to get combination of actions cut plastic slowly to get heat to round the edges
22 blessing in disguise; turn lemons into lemonade curse in disguise; turn sugar into vinegar good tasting rat poison
23 feedback lack of feedback; uncontrolled; positive feedback (feed forward) random number generator; random noise generator for white noise in office
24 intermediary remove intermediary; simplify; self-service (#25) hammer with small head for small nails; agree on one file format; dish or pan with insulated handle so you don't need a pot holder
25 self-service single purpose device; intermediary (#24) keep a key part separate so additional attention must be paid for safety - book matches vs kitchen matches
26 copying avoid copies; use original  
27 use cheap replacement objects use expensive replacements, use expensive original rechargeable batteries
28 substitution for mechanical means substitution by mechanical means  
29 pneumatics and hydraulics mechanical use a flywheel to store energy
30 flexible shells and thin films rigid shells and thick slabs make 2x4 wall instead of tent; hard-sided collapsible camper vs covered wagon
31 porous materials impermeable materials add wax coating on paper to make milk carton; add clay to paper to make better printing; put skin on foam to prevent water uptake; closed cell vs open cell foam
32 color changes use monochrome systems, use negative images use black & white instead of color to simplify image processing
33 homogeneity heterogeneity use softer rubber for tires for better traction; brake pads designed to wear; sacrificial anode for metal protection
34 discarding and recovering this is its own opposite  
35 parameter changes parameter constancy plastic food containers usable in oven; alcohol thermometer for low temps; silicone gaskets work over wide temperature range
36 phase transitions phase stability  
37 Thermal expansion dimensional stability match expansion coefficients of composite to avoid distortion
38 strong oxidants strong reducers use catalytic converter to reduce NOx using unburned HC; use hydrogen to crack petroleum components; use reducing atmosphere for specialized welding
39 Inert atmosphere active atmosphere; presence of atmosphere; take away neutral parts; add active parts remove water from product to make cheaper to ship; add magnetic particles to plastic to make microwave heatable
40 composite materials monolithic materials molded-in color so no painting is necessary



  1. The Invention Machine Co. TechOptimizer
  2. H. Altshuller, Forty Principles, Translated by Lev Shulyak. Technical Innovation Center, Worcester, MA. 1998
  3. H. Altov (Altshuller pseudonym), And Suddenly the Inventor Appeared, translated by Lev Shulyak, Technical Innovation Center, Worcester, MA. 1996
  4. J. Terninko, A. Zusman, B. Zlotin, Step-by-Step TRIZ. Responsible Management, Durham, NH, 1997
  5. E. Domb. "Contradictions" The TRIZ Journal, July, 1997,
  6. H. Altshuller. Creativity as an Exact Science, Translated by Anthony Williams. Gordon & Breach, NY. 1988