Presentation on theme: "Section 3.7 Teleology Naturalized. Questions 1. What is teleology? 2. Why are we striving to escape from it? 3. What are the remnants of teleology in."— Presentation transcript:
Questions 1. What is teleology? 2. Why are we striving to escape from it? 3. What are the remnants of teleology in biology? 4. What are the possible explanations of biological teleology? 5. How can we naturalize biological teleology?
What is teleology? Teleology is a form of explanation: – Teleology explains phenomena by referring to purposes, ends, aims, etc. Teleology is an answer to “why?” and “what for?” questions: – Why do birds have wings? – Why do we have eyes? – What are cell phones for?
What is teleology? Teleological explanations versus mechanical explanations: – Q: Why does rain fall? – M: Rain falls because evaporized water condenses when temperature decreases and its density increases. Hence, the gravitational force over water drops exceeds ascending force of air. – T: Rain falls in order to water crops and nourish living things.
What is teleology? Some historical preliminaries of teleological explanations: – Plato: Everything was created by demiurgos. Since demiurgos (god) created everything for a reason, everything is at its best: – “This ordered world is of mixed birth; it is the offspring of a union of Necessity and Intellect. Intellect prevailed over Necessity by persuading it to direct most of the things that come to be toward what is best, and the result of this subjugation of Necessity to wise persuasion was the initial formation of this universe (Timaeus, 48a trans by Zeyl).”
What is teleology? Aristotle’s teleology: – Like moves to like: For instance, a stone falls toward the center of earth because they are both made up of same essential ingredients. – Development of organisms from birth to adulthood is guided by an intrinsic purpose. The adult organism is the purpose of development. – Functional parts of organisms exist because of their benefits to their possessors. – Pure chance can not explain the order we observe in organic and inorganic worlds.
Why are we striving to escape from teleology? Findings of the sciences eliminated teleological explanations from many fields of science: – Newtonian physics explains movements of objects without referring to purposes: – There is no purpose of a stone which falls down to earth. It just obeys a law of nature. – Nature is not perfectly ordered. For instance, planets do not follow circular orbits as once imagined by ancient Greeks. – Earth is not the center of the universe. Hence, the universe is not centered around humans.
What are the remnants of teleology in biology? Functions and functional explanation: – Functional explanation is a remnant of teleological talk because by assigning functions to objects we answer a “what for” question. – For instance: “What is the function of DVDs?” can be translated as “What are DVDs for?” – In the case of artifacts, there seems to be no interesting problem. Artifacts are produced or used for specific purposes: DVD’s are produced and used for storing digital information.
What are the remnants of teleology in biology? What about biological traits? – What is an hemoglobin molecule for? Is this question a legitimate one? Can you sense any problem about this question? – The problem is that hemoglobin molecules are not designed by intelligent agents like humans. – When we say that “the function of hemoglobin molecules is to carry oxygen to tissues” we must be meaning something else.
What are the possible explanations of biological teleology? Creationist Explanation: – An omnipotent God created all living things at once. Since living things are products of an intelligent being, functions they possess reflect God’s intentions. – In other words, we must analyze living things just as we analyze artifacts. “What for?” questions are legitimate questions. – For instance: What is hemoglobin for? can be answered by the statement “It was designed by God to carry oxygen to tissues.”
What are the possible explanations of biological teleology? What is wrong with the creationist approach? – If we are to explain complexity and order in nature, we should do it by using simpler means. Even if we solve the problem of explaining natural order, we need to explain how God achieved his aims. The concept of God needs explanation too. – Organic world is full of imperfect adaptations. – We can observe the change in the living world even in our lifetimes. Think of the evolution of HIV in a few decades.
What are the possible explanations of biological teleology? Darwinian Explanation – Functional traits of organisms are products of a lengthy chain of natural events. The totality of these natural events is called natural selection. – What is natural selection? – Organisms in a population may have different traits: Birds have differing wing lengths, bacteria have differing capacities of antibiotic resistance, humans have different eye colors, etc.
Darwinian Explanation What is natural selection? – Some of these differences are heritable. For instance, resistant bacteria have resistant offspring, tall parents have tall children, etc. – These heritable differences affect reproduction rates of their owners. For instance, resistant bacteria produce more offspring, tall parents produce greater a number of children, long winged birds have more offspring, etc.
Darwinian Explanation What is natural selection? – Having more offspring changes the composition of the population in favor of fitter organisms. The fitter trait increases in the population. – The function of a trait is the effect which helped the trait to spread: The function of hemoglobin is binding oxygen because binding oxygen is the effect which caused the spread of hemoglobin carrying organisms.
Darwinian Explanation Some conceptual distinctions: – Adaptations versus adaptive traits : Adaptation refers to a product of natural selection. A product of natural selection may or may not have current utility. An adaptive trait is currently beneficial to the organism. – For instance hemoglobin binds CO with a greater affinity than it binds to oxygen. CO is a toxic agent. In some circumstances, having hemoglobin may be detrimental to the organism. But it is still an adaptation. – Adaptation is an historical concept, whereas adaptiveness is not.
Darwinian Explanation Some conceptual distinctions: – Ontogenetic adaptation versus phylogenetic adaptation: – Ontogenetic adaptation: Adaptive changes that occur during the lifetime of an organism. For instance, a human infant’s learning how to deal with physical objects is an ontogenetic adaptation. – Phylogenetic adaptation: Adaptive changes that occur during the genesis of a species. For instance, the growth in brain size of primate lineage resulting in humans is a phylogenetic adaptation process.
How can we naturalize biological teleology? Etiological theories of function: – Proponents of etiological theories claim that functional explanations anwer the question “why is trait x present?” – Etiological theories try to demarcate accidental effects from genuine functions. For instance, hearts make thumping noises besides pumping blood. We don’t want to ascribe functions to such accidental effects. But we need a ground to distinguish functions from side-effects. – The ground for that distinction is provided by designer and user intentions in the case of artifacts. For instance when we ask “what is the function of that fan in my computer?” we are asking why did the engineer put that fan in that specific location.
How can we naturalize biological teleology? Etiological theories of function: – In the case of organic functions we explain the presence of the trait by referring to a specific effect that led to the selection of the trait. – For instance “the function of hearts is to pump blood” can be justified by the statement “the effect that lead to the spread of hearts in an ancestral population was their ability to pump blood”. – This way, we may demarcate functions from accidental effects: Making thumping noises is not a function of hearts because hearts are not selected for that effect.
How can we naturalize biological teleology? Causal-role theories of function – Function ascriptions do not need to be historical hypotheses. – The aim of function ascription is to analyze complex systems into simpler parts. – Function=the contribution of simpler parts to a systemic capacity. – For example, when we ask “what is the function of that fan in my computer?” we are in fact asking “what contribution does that fan make to the working of that computer”
How can we naturalize biological teleology? Causal-role theories of function – Flowchart diagrams, abstract descriptions of electronic circuits or assembly lines are best examples of this approach. Consider the computer fan example I mentioned before. The function of the fan is to cool the processor. Cooling the processor is a capacity of the computer which is achieved by the inner workings of the fan. The fan can be decomposed into its simpler parts. These simpler parts contribute to the cooling capacity of the fan, hence, one can explain how the cooling capacity of the computer is realized by means of analyzing relevant parts into simpler and simpler capacities they have.