Is science based on observation?

0.1 Science and observation

Let’s suppose that science is based on observation. That is, suppose that scientific knowledge is based on an unprejudiced derivation of knowledge and theory from information given directly to the senses (facts). This information (“the facts”) is:

  1. directly given via the senses (sight, touch, taste, etc.)
  2. temporally prior to and do not depend upon theory and do not depend (in any way) upon bias, prejudice, desires
  3. passively received
  4. the foundation for scientific theory: scientific theories and knowledge are built on the basis of these facts.

In saying that facts are given directly via the senses, what is being said is that indisputable information about the world can be gathered simply by recording what is given to us by our senses. We have direct access to singular bits of information through our five senses. One common view of science then is scientists have sensory experiences and create scientific theories out of these experiences. Sensory experience (ideas) are thought to be the origin and/or foundation of all knowledge. This view might be called “naive empiricism”:

Definition 1 (naive empiricism) Empiricism is the view that all of our knowledge is based on experience.

Every man being conscious to himself, that he thinks, and that which his mind is employed about while thinking, being the ideas, that are there, ’tis past doubt, that men have in their minds several ideas, such as are those express by the words, whiteness, hardness, sweetness, thinking, motion, man, elephant, army, drunkenness, and others: it is in the first place then to be enquired, how he comes by them? I know it is a received doctrine, that men have native ideas, and original characters stamped upon their minds, in their very first being. This opinion I have at large examined already; and, I suppose, what I have said in the fore-going Book, will be much more easily admitted, when I have shown, whence the Understanding may get all the ideas it has, and by what ways and degrees they may come into the mind; for which I shall appeal to every one’s own observation and experience.

Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas; how comes it to be furnished? Whence comes it by that vast store, which the buy and boundless fancy of man has painted on it, with an almost endless variety? Whence has it all the materials of Reason and Knowledge? To this I answer, in one word, from Experience: In that, all our knowledge is founded; and from that it ultimately derives it self. Our observation employed either about external, sensible objects; or about the internal operations of our minds, perceived and reflected on by our selves, is that, which supplies our Understandings with all the materials of thinking. These two are the fountains of knowledge, from whence all the ideas we have, or can naturally have, do spring. –John Locke, An Essay Concerning Human Understanding, Bk II, Ch I, §1-2

It is evident to any one who takes a survey of the objects of human knowledge, that they are either ideas actually imprinted on the senses, or else such as are perceived by attending to the passions and operations of the mind, or lastly ideas formed by help of memory and imagination, either compounding, dividing, or barely representing those originally perceived in the aforesaid ways. — George Berkeley, The Principles of Human Knowledge, Part I

Discussion 1 Both Locke and Hume base all knowledge on experience, but both do not take this simply to mean sense experience. What other type of experience do they refer to?

0.2 Criticisms

Objection 1 (Observation and illusion) If scientific knowledge and theories are based on observation, it is observations of a certain type. That is, scientific theories are purportedly not based on sensory information known to be illusory (e.g. optical illusions). However, sorting out what is and isn’t an illusion can be difficult. In determining what is and is not an illusion, we rely upon our existing beliefs about the world (the theories that we accept). However, if the theory that we accept is wrong about the world, then it may wrongly lead us to treat certain observations as illusions.

For example, it was previously thought (drawing from Aristotle) that the moon (and all objects in the heavens) was a perfect sphere. If one looks up at the full moon with the naked eye, it does not appear to have any craters or mountains. In addition, celestial bodies were also claimed to be perfectly spherical on the basis of their nature:

Being ingenerable, incorruptible, inalterable, invariant, eternal, etc. implies that celestial bodies are absolutely perfect; and being absolutely perfect entails their having all kinds of perfection. Therefore, their shape is also perfect; that is to say, speherical – and absolutely and perfectly spherical, not approximately and irregularly – Galileo Dialogue 84, qtd in Drake, Stillman Galileo: A Very Short Introduction, p.54.

However, Galileo observed with a telescope that the moon does have mountains and craters, and he used various methods used by surveyors to determine the size of these mountains. His observations went against accepted theory about the celestial bodies in general and the moon in particular. In reaction to the report of these discoveries in Galileo’s Starry Messenger, astronomers and philosophers claimed that (i) the mountains and craters were optical illusions and (ii) there was no proof that what Galileo claimed to see was anywhere except in the lenses of the telescope itself.

Objection 2 (Observation is not passive) The view of science characterized above has it that we are given information by merely opening up our eyes. With this information, we build up scientific theories. First, this ignores a certain active element of observation, e.g. squinting, focusing, scanning, etc. In addition, it ignores that scientists actively manipulate and control the settings so they can “see better”

Objection 3 (Errors in Perception: Biology) What we perceive and what we know about sensation indicates that much of what we perceive is added by the mind.

Example 1 (the blind spot) The blind spot is the location on the human retina where the optic nerve fibers exit the back of the eye. Since there are no rods or cones at this location, there is a small, unnoticeable gap in the visual field.

Example 2 (depth) We don’t immediately see the distance of an object from ourselves. Instead, we unconsciously infer it from a variety of visual cues. In other words, there is no immediate perception of depth.

Objection 4 (Perceptual experiences are ambiguous.) To see exactly how a single retinal image can be interpreted ambiguously, consider the Rubin vase (see Figure 1.). When staring at the Rubin vase image, observers see the same retinal image (they have the same sensation), but this image is consistent with two different perceptual experiences (two vases or a single vase).


Figure 1: A Rubin Vase is an ambiguous image created by the Danish psychologist Edgar Rubin. The vase presents observers with a single retinal image whose interpretation is consistent with one of two objects (vase or two faces).

Objection 5 (Perception colored by prior experience.) In the case of the Rubin vase, it is relatively easy to switch back and forth between the two images. There are some examples where individuals only see one image and this image is determined by their prior experience. For example, consider the jug in Figure 2.


Figure 2: “This image was also displayed in an illusion exhibit gallery at the Museum of Science in Boston. When asked if there was any controversy about displaying the image, the curators replied that once a group of nuns had objected, but were quickly silenced when told that one’s perception is based on past experience.”

The jug determines a single retinal image but produces different perceptual experiences according to one’s prior experience. Children, for example, tend to only see dolphins on the jug, while adults see a provocative scene.

Objection 6 (Perception colored by expectations.) In addition to ambiguous images, individuals often misinterpret images that are contrary to their expectations. For example, in an experiment, twenty-eight subjects were shown successively five different playing cards. Cards were of two sorts: normal cards and trick cards, the latter being cards where color and suit were reversed. One to four of the five cards shown to subjects were trick cards, e.g. two of spades (red). Subjects were exposed to cards at varying intervals, 10ms, 30ms, 50ms, 70ms, …, 1000ms until they were able to correctly identify the card.

Subjects had roughly four different reactions:

This study showed that it took longer for subjects to recognize trick cards than normal cards (28ms vs. 114ms).

The point is that oftentimes when we are viewing something that is contrary to our expectations, there is a longer threshold to accurately recognize what is perceived. So, if we don’t have time to examine it long enough, we can misidentify what we have perceived (compromising / dominance). This has implication for how the biases we have shape our perception.

Objection 7 (Perception and context) Some objects of perception are only seen when information or context is given about the object. In other words, the object is not an intelligible object unless someone tells us how to see it. That is, we need knowledge about the object in order to understand what we are looking at.

For example, someone unfamiliar with Jesus Christ might not recognize his face in a blob-looking image in a napkin. In scientific practice, prior experience influences our perception. An expert technician is able to tell you whether some spot on an x-ray is cancer or an apparition (or something else). When one is trained to look through a microscope or a telescope, a trained individual sees something different (something more intelligible) than the lay person. A child might look at an x-ray tube and see a light bulb, but an engineer would see something different. In each case, individuals can be said to “see” something that an untrained observer cannot.

Objection 8 (facts are not always prior to theory: concepts) We need a conceptual framework to even formulate certain facts and to categorize objects. If we see an apple, we need some preliminary concepts and information to say “that is red, that is an apple, etc.”

Objection 9 (facts often depend upon the accepted scientific theory) The claim that the “the earth is stationary” may be said to be a fact before the Copernican revolution. Consider that observation prior to that time confirmed it. If I am standing here, I don’t feel or see the earth move.

Copernicus, however, argued that the earth is not in a state of rest but in a state of constant motion around the sun. One problem with this was how to explain the fact that we don’t feel that we are in a state of motion. That is, if the earth is spinning at around 1000mpw, why don’t we feel it? Galileo argued that the concept of inertial motion could explain why we don’t feel we are moving. That is, we don’t feel the earth moving because it is moving at a constant velocity.

A second example involves the appearance of Venus and Mars. Venus and Mars should look different depending upon where the Earth is in its orbit, but to the naked eye they always appear the same size.