Scientific Revolutions: Historical Perspective

Scientific Revolutions: Historical Perspective Back to the Roots:Greek Science

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology Main Themes: The demythologization of nature The idea of a cosmos The search for general explanations Man as a spectator Critical debate Consistency Appearances vs. Reality Permanence and Change

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology The Ionians: Thales of Miletus (c. 624-547 B.C.): “All is water”. Anaximander of Miletus (610-545 B.C.): “The basic stuff of the Universe is the ‘apeiron’.” Anaximenes of Miletus (588-524 B.C.): “The basic stuff of the Universe is air”. Heraclitus of Ephesus (540-480 B.C.): “The basic stuff of the Universe is fire”.

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology The Ionians: "Nothing endures but change.” Heraclitus: “No man can cross the same river twice, because neither the man nor the river are the same”.

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology The Italian School: Pythagoras and the Pythagoreans(c. 550-500 B.C.): • A “number” cosmology • "Save the appearances" in astronomy • The notion of proof in mathematics • The discovery of irrationals

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology The Eleatic School: Parmenides of Elea (c. 500-450 B.C.): Being, is One, Indivisible and Unchanging. What is One cannot be or become many. What is, is immovable, since motion requires a void, but a void is nothing, and, hence, does not exist.

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology The Eleatic School: Parmenides of Elea (c. 500-450 B.C.): All change, including apparent temporal and spatial change, as well as the apparent diversity of the sensible world are illusions--mere appearances.

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology The Eleatic School: Zeno of Elea (@ 460 B.C.): The paradoxes: Achilles and the Tortoise: In a race, the quickest runner can never overtake the slowest, since the pursuer must first reach the point whence the pursued started, so that the slower must always hold a lead.

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology Reactions to the Eleatic School: Empedocles (@ 490-430 B.C.): • The theory of the four elements: • Water, earth, air, fire. • Love (philia) and Strife (neikos) explain the attraction and separation of different forms of matter.

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology Reactions to the Eleatic School: The Atomists: Leucippus (fl. 430 B.C.) and Democritus (460-370 B.C.) • Yes, what is cannot come into being or perish. • But the universe contains an infinite number of such indestructible beings, "atoms." "Nothing exists but atoms and the void."

The pre-Socratics (600-400 BC):The Birth of Rational Cosmology Reactions to the Eleatic School: The Atomists: Leucippus (fl. 430 B.C.) and Democritus (460-370 B.C.) • Space is infinite in extent. • Space is an objective feature of the world. Even if human perceivers did not exist, space would still exist. Space is "mind-independent." • Hence, void (i.e., space) is "object independent." • Space (as void) is not continuous, since where atoms are, void is not.

Disciple of Socrates The Legacy of Plato (429-348 B.C.) • Founder of the Academy in Athens • "Let None Ignorant of Geometry Enter Here."

Main Socratic Dialogues The Legacy of Plato (429-348 B.C.) • Apology • Charmides • Gorgias • Meno • Protagoras • Republic • Parmenides • Theaetetus • Timaeus • Sophist • Philebus • Laws

The problem of Permanence and Change The Legacy of Plato (429-348 B.C.) • The World of Forms • The World of Appearances

The problem of Permanence and Change The Legacy of Plato (429-348 B.C.) • The World of Forms • A world of permanent unchanging essences or true Beings. True knowledge of these Forms is possible through the use of reason.

The problem of Permanence and Change The Legacy of Plato (429-348 B.C.) • The World of Appearances (sensible world) • The world of everyday life and experiences. Its objects are subject to constant change. It is a world of Becoming. It is not itself “completely real”.

The problem of Permanence and Change The Legacy of Plato (429-348 B.C.) • The World of Appearances (sensible world) • It is not itself “completely real”? • Like a picture, the object “participates” of its real form, but it is not identical to it.

Plato’s Cosmology (Timaeus, a creation myth) The Legacy of Plato (429-348 B.C.) • The universe, or Cosmos, is a living being endowed with a soul. The Cosmos was fashioned from a pre-existing chaos by a Divine Craftsman, the Demiurge, using the Forms as models for sensible objects.

Plato’s Cosmology (Timaeus, a creation myth) The Legacy of Plato (429-348 B.C.) • The four-elements theory • The Cosmos is a self-contained sphere which, although alive, does not need any nourishment, since otherwise it would be subject to decay. The sphere uniformly rotates on its axis with the earth at the center. Uniform circular motion is the motion most fitting for a rational being, the closest it can get to not moving at all--i.e. the closest it can get to its eternal archetype.

Plato’s Cosmology (Timaeus, a creation myth) The Legacy of Plato (429-348 B.C.) • The earth, at the center, rotates with the sphere. In order to preserve the succession of day and night, as observed from the earth, the earth must have a counterrevolution. All the planets, including the earth, are gods, and each has a motion proper to it.

Plato’s Cosmology (Timaeus, a creation myth) The Legacy of Plato (429-348 B.C.) • The diurnal motion of the heavens around the earth is produced by what Plato calls "the motion of the Same". A further motion, the motion of the Different, is in the opposite direction and at an angle to the motion of the Same. The path of the motion of the Different is through the ecliptic, which is that portion of the sky which contains the orbits of the sun, moon and planets. The motion of the Different accounts for the tendency of these bodies to rotate, with respect to the Earth, in the opposite direction to the daily motion of the stars.

Different in the opposite direction and at an angle to the motion of the Same, through the ecliptic.

Plato’s Cosmology The Legacy of Plato (429-348 B.C.) • The four elements, well … they are actually five:

Plato’s Philosophy: • Strong presence of mythical elements • Strongly rationalist • Realist of ideas • Central place to mathematics Aristotelian Philosophy of Nature: • Strongly empiricist • “Common Sense” empiricism • Little concern with mathematics

Disciple of Plato The Legacy of Aristotle (384-322 B.C.) • Preceptor of Alexander the Great • Founder of the Lyceum in Athens • ”Nothing is in the intellect that was not first in the senses.” • (according to Aquinas)

Aristotelian Philosophy of Nature His innovative reply to the Eleatics: The actual vs. the potentialBeing-in-act vs. Being-in-potency. • The former may arise from the latter.

The figure of the statue is in potency in the block of marble. This potency is not nothing, it is not non-being. It is real; not with the reality of being-in-act, but with the reality which corresponds to being-in- potency.

The shape of the sculpture is the form that comes to be when a formless block of marble becomes a statue. The formlessness of the block is itself the privation of the statue shape, and the potency for the statue shape. The marble, first in block shape, later in "David" shape, is the matterthat stays the same throughout the change. The case of the coming-to-be of a statue is an instance of an accidental change; what changes are the accidents of the marble. What stays the same is the substance of the marble.

Aristotelian Philosophy of Nature Three principles involved in change: • Something new that comes to be (form), • Something old that passes away (privation), • Something that stays the same throughout (matter)

Aristotelian Philosophy of Nature Aristotle (Physics): three classes of motion (accidental change) • In place (local motion), • In quantity, or size (growth-diminution), • In quality (alteration)

Aristotelian Philosophy of Nature • Motion is the process that a substance goes through in which it loses one accidental form and gains another. • Motionis the act of something that does not yet have, but is acquiring, the full act of a new accidental determination, a new quality, size or position.

Aristotelian Philosophy of Nature • Substantial change: involves the coming to be or passing away of a substance. • Example: Sodium and Chlorine into Salt • Also here: matter (sodium and chlorine), form (salt) and privation.

Aristotelian Philosophy of Nature • Aristotle’s four causes: needed to explain change. • Material – Formal • Efficient – Final

Material cause: • Prime matter - Four elements • Four basic Qualities: Hot, Cold, Wet, Dry • Secondary Qualities: color, sound, smell, taste HOT AIR FIRE WET DRY WATER EARTH COLD

Formal cause: not necessarily a shape. • “In the case of living things, it is very clear that to explain behavior we must refer not to surface configuration, but to the functional organization that the individuals share with other members of their species. This is the form; this, and not the shape remains the same as long as the creature is the same creature. The lion may change its shape, get thin or fat, without ceasing to be the same lion; its form is not its shape, but its soul, the set of vital capacities, the functional organization, in virtue of which it lives and acts.... "

Formal cause: not necessarily a shape. • “A corpse has the same shape as a living man; but it is not a man, since it cannot perform the activities appropriate to a man … . When I ask for the formal account of lion behavior, I am not, then, asking just for a reference to tawny color or great weight. I am asking for an account of what it is to be a lion: how lions are organized to function, what vital capacities they have, and how these interact. And it is this, again, rather than an enumeration of its material constituents, that will provide the most simple, general, and relevant account for the scientist interested in explaining and predicting lion behavior. (cf. PA 641a7-17)"

Efficient – Final cause: • Efficient causes initiate processes and bring about their effects. Final causes account for processes and entities by being what these processes and entities are for, what they objectively intend to attain.

Efficient – Final cause: • In forced motion there is an external mover: it has to be in contact with the moved body. • In natural motions the efficient cause of the motion is internal: the natural form of the thing that changes.

Efficient – Final cause: • For Aristotle natural bodies tend to their natural place (fire tends up, earth tends down). The internal source for the motion of growth for all living things is soul. Animals have the further motions of local motion and sensation, and the efficient cause of these motions is also soul.

Aristotelian Philosophy of Nature Genus – Differentia Man: Rational Animal

Limitied in size (since it has a center) • No void in nature • Sub-Lunar vs. Supra-Lunar • Planets move in circles

Scientific Revolutions: Historical Perspective