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HERAUSGEGEBEN VON WERNER D'INKA, BERTHOLD KOHLER, GÜNTHER NONNENMACHER, HOLGER STELTZNER

Logik mit Unschärfen Fuzzylogik in Wissenschaft, Recht und Ethik

Dem Ideal der klaren Entscheidung zeigt die trübe Wirklichkeit rasch Grenzen auf. Ein medizinisches Gedankenspiel illustriert, wie die alternative Fuzzylogik funktioniert.

© AFP Vergrößern Entweder „Evet“ (dt. „Ja“) oder „Hayir“ (dt. „Nein“)? Anders als dieses Verfassungsreferendum im September 2010 in Ankara konzentriert sich die Fuzzylogik auf Zwischenwerte

In 2006, after a remarkable increase in births of extremely premature newborns, the United Kingdom-based Nuffield Council on Bioethics recommended: “intensive care should not be given to babies born before 22 weeks, and babies born between 22 and 23 weeks should not, in normal practice, be given intensive care unless parents make a request and doctors agree” (pdf-link).  The above-mentioned recommendation was based on data indicating that of babies born prematurely between 22 to 23 weeks only 1% survived, and that the survivors faced the added risk of developing severe disabilities. A question that may be raised is whether such a recommendation is sufficient to relieve people of the stressful and painful feelings that such serious ethical dilemmas can provoke.

The more biotechnology and medical sciences evolve, the more the associated ethical dilemmas and, consequently, the more regulations with regard to how to solve such dilemmas. Even though such regulations may be formulated to help us to surpass the difficulties associated with facing a dilemma, in fact, they have been shown to complicate matters further. The cause of this type of thorny situation is that laws or other rules of conduct mirror a societal attempt to render things precise, specific and certain, overlooking the fact that almost everything around us is ruled by indeterminacy, fuzziness and uncertainty. Laws are mostly founded on the idea that everything must be either true or false. To a legislator, a thief either stole an item or did not; a doctor either resuscitated a premature newborn baby or did not. In other words, to the legislator human actions reflect absolute values.

Expanding the Limits Of Human Logic

However, the view that reality can be described and assessed in an absolute manner has been put into doubt. For much of history, people were using absolute, “yes or no” type propositions in order to describe reality. For example, as in the proposition “it’s raining”, or its negative “it’s not raining”. Using this type of approach, something is either true or false. However, at the beginning of 20th century, appeared the idea that something may be uncertain or vague; for example, this is so when we refer to something in the future. When referring to the future people typically use propositions that are neither true nor false; instead, their propositions are uncertain or vague.

The introduction of the notions of uncertainty and vagueness has allowed people to expand the limits of human logic; thereby, paving the way to an enhanced perception of reality and to a logic foundation that includes the notions of certainty, truth and falsehood. This is how the concept of fuzzy logic emerged. It is based on the idea that, in some cases, the truth is not a yes or no issue but is a matter of degree. Using that logic, reality ranges over all shades of colour between black and white; that is, reality includes many degrees of the truth.

What Should The Doctor Do?

To appreciate the significant contribution of fuzzy logic to everyday life, consider a doctor who is facing the dilemma of whether to resuscitate a premature baby. A decision based on the absolute principles of a bivalent logic system must be a yes or no decision. As it is extremely rare for babies born before 22 weeks to survive and even if they survive it is likely that they will develop such great disabilities that many people would not judge their life to be worth living. However, how feasible or ethical is it to treat all neonates born before 22 weeks in the same way when a general regulation requires it?

Strict compliance with the general regulation requiring that “premature babies born before 22 weeks should not be resuscitated” may ignore important factors. For example, do we follow the regulation for a baby with an age of 22 weeks minus one day? Moreover, the health condition of a premature baby of 21 weeks may better than the health condition of a baby of 23 weeks or a situation in which, of two premature babies, the younger is responding better to a treatment. If fuzzy logic is used, what ought the doctor to do under such circumstances.

Mehr zum Thema

However, some might suggest that the main duty of a doctor is to treat every situation in an absolute manner, without participating in excessive, fuzzy considerations. The existence of rules and regulations provides support to that approach. However, others suggest that the application of fuzzy logic in our life favours a less rigid, more flexible way of facing ethical problems or dilemmas.

Consider the following cases: one doctor complies with the regulations of a bioethical council and decides not to resuscitate a premature baby born before 22 weeks, while a second doctor makes the same decision following an exhaustive examination of the situation. Which doctor is considered to have acted more ethically? To many, it is the one who came to a decision after having exhausted all of the available resources. Such an outcome is more possible when using fuzzy logic rather than when using traditional bivalent logic with its absolute, black and white approach to questions.

 
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Veröffentlicht: 26.01.2013, 06:22 Uhr

Berliner Zukunft

Von Christian Schwägerl

Gas geben oder bremsen - wofür entscheidet sich die Bundesforschungsministerin? Sie kann es sich aussuchen, in welche Art von Innovationen sie ihre stattlichen 14 Milliarden Euro anlegt. Ein Vorausblick in den Foresight-Bericht. Mehr 4