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Summary

Dramatis personae

Dates of birth and death given below are conjectural, except for Socrates.

CALICLES His boyfriend Demos, son of Plato's stepfather Pyrilampes, was in Dodds's words (Plato: Gorgias, p.261, relying here primarily on Aristophanes' Wasps 98) ‘a leading beauty about 422’. On usual assumptions about relative ages of lover and beloved, we might infer that Callicles was probably in his mid to late twenties at the same point in time. Although his ambition to succeed in politics makes Socrates describe him as lover of the Athenian demos (punning on Demos), this behaviour must be interpreted as opportunistic on Callicles' part. The views Plato attributes to him are anything but democratic. And it is probably significant that of the friends of Callicles mentioned at 487c, one at least – Andron – is known to have been a member of the short-lived oligarchic regime of the Four Hundred in 411, and the other two probably to be identified with Athenians known from other evidence to have been wealthy men. There is no trace of Callicles in history outside the Gorgias. It seems likely that for whatever reason his ambitions were unfulfilled.

CHAEREPHON (467–401) One of Socrates' oldest and closest friends, and a well-known figure in the Athens of the Peloponnesian War, frequently the topic of jokes on the comic stage, perhaps in part because of his demonic energy (Apology 21a, Charmides 153b).

Summary

The translation (by TG) is made in the case of Gorgias from the text in Dodds's edition, and in the case of Menexenus and Protagoras from Burnet's edition in the Oxford Classical Texts series. The few variations from these adopted here are mentioned in notes at the appropriate points. The notes to the translation (by MS, as with the rest of the editorial matter) have benefited in various ways from TG 's scrutiny, and the translations in their final form are the outcome of several rounds of comment from MS and rethinking by TG. Raymond Geuss and Quentin Skinner as series editors made suggestions for improvements to the draft of the introduction, all gratefully implemented. The book is therefore very much a joint production, which owes its origins to a suggestion by Jeremy Mynott, at the time Chief Executive of the Press – to whom also thanks are due.

Summary

The Gorgias and the Protagoras

The Protagoras and the Gorgias are not only the longest, but by general agreement the most important among Plato's ‘Socratic’ dialogues (the quixotic Menexenus – on which more later – is another matter). Both present Socrates in argument with leading members of the sophistic movement, questioning the claims to wisdom or expertise that they make. In both Socrates brings the discussion round to his own central preoccupation with living a good life.

But there the resemblances cease. One difference is purely formal. The Gorgias (like the Menexenus) is written as drama, with parts for Socrates, Gorgias, and various other characters, notably Polus (a follower of Gorgias who has authored a book on rhetoric) and Callicles (apparently a rising young Athenian politician). There are few indications of time or place. For the Protagoras, Plato elected for a more complex structure, beginning with a short exchange in direct dramatic form between Socrates and an unnamed companion, which then frames a lengthy report by Socrates, full of circumstantial detail, narrating an early morning visit from a young friend called Hippocrates, and their subsequent encounter with Protagoras and other sophists at the house of the wealthy aristocrat Callias.

The major difference is one of tone. Plato's writing in the Gorgias has little of its usual urbanity.

Summary

Simonides' poem reconstructed

Truly becoming good is hard for a man,

Standing four-square with hands and feet and mind,

Fashioned beyond reproach.

(Missing lines)

It strikes a wrong note,

That saying of Pittacus – though wise the man

Who spoke it – ‘Being good,’ he said, ‘is hard.’

Only a god can have this privilege.

He cannot but be bad, a man, when once

Helpless disaster brings him down.

For any man is good when things go well,

But bad when they go ill.

Best for the longest time are they – whom the gods love.

I will not cast my life's portion away

In hopeless quest for what can never be –

A man who's blameless among those who reap

The broad earth's harvest.

Should I find one,

I'll bring you word.

All those who do no shameful action willingly

I praise and love.

Against necessity not even gods can fight.

(Missing lines)

Enough, for me,

A man who is not bad, not wholly useless,

A sound and healthy man, one who well knows

Justice, the city's profit, I will not

Blame him.

The tribe of fools is numberless –

All things are fair wherein no foul is mixed.

Summary

Dramatis personae

Dates of birth and death given below are conjectural, except for Socrates and for the deaths of Alcibiades and Critias.

ALCIBIADES (451–404) Flamboyant Athenian aristocratic politician, brought up in Pericles' household as his ward. An associate of Socrates from an early age: Socrates' erotic interest in him is explored in the Symposium, and alluded to in both the Gorgias and the Protagoras. He was the main advocate and initially commander of the Sicilian expedition (415–413), but was indicted in connection with religious scandals and recalled from his command. After intriguing first with the Spartans and then the Persians, he subsequently led the Athenian fleet to victory over the Spartans at Cyzicus in the Bosphorus (410). After further personal vicissitudes, he was murdered by Persian agents in Phrygia (modern Asiatic Turkey).

CALIAS (450–365) His father Hipponicus was an Athenian aristocrat reputed to be the richest man in Greece and still active in the 420s (he served as general in 426/5). The family were connected to Pericles' family by marriage. Following the precedent of Eupolis's comedy Sycophants (421), Plato here imagines Callias as a mature man who has recently inherited the principal family house (315d) and is lavishing his wealth on sophists (see further Apology 20d). We hear of Callias as a public figure in his later years (general, 391; diplomatic envoy, 371).

Summary

Dramatis personae

MENEXENUS With his cousin Ctesippus became a member of Socrates' intimate circle, to judge from their presence in the prison on the day the hemlock was administered (Phaedo 59b). In the Lysis Menexenus (again in Ctesippus's company) and his friend Lysis are boys of twelve or thirteen. In the Menexenus he is evidently a few years older. Socrates suggests that he came from a prominent political family – but history has left no clues enabling us to identify the public figures Plato might have had in mind.

SOCRATES (469–399) Sustains throughout the dialogue the teasing pretence that he is currently a student of rhetoric, with Pericles' mistress Aspasia for his teacher. What purpose Plato had in representing him in this alien and improbable guise is discussed in the Introduction.

Analysis

234a–236d – Introductory conversation

236d–249c – Speech of Aspasia

236b–237b Introduction

237b–238b Good birth and upbringing: Athenian autochthony and how it shapes the life of the population

238b–239a Good upbringing: the Athenian political system

239a–246b Noble exploits: Athenian history

Summary

Introduction

In this chapter, we set the scene for the rest of the book. It may be helpful to remind readers of the relevance and importance of soil mechanics for all civil engineering construction: everything we construct sits on the ground in some way or other at some stage in its life. Even aircraft land on runways, and cars drive along roads; in each case there is some stiff layer (pavement) between the wheels and the prepared ground underneath. This stiff layer will help to spread the vehicular load but, in the end, this load must still be supported by the ground. Some examples of typical geotechnical design problems are presented in the next sections.

The term soil mechanics refers to the mechanical properties of soils; the term geotechnical engineering refers to the application of those mechanical properties to the design and construction of those parts of civil engineering systems which are concerned with the active or passive use of soils. Soils are the materials that we find in the ground: the term ground engineering is somewhat equivalent to geotechnical engineering. We will talk a little about the nature of soils in Chapter 3.

The term soil means different things to different people. To an agricultural engineer, the soil is the upper layer of the ground which the farmer ploughs and harrows and in which crops are sown.

Summary

Introduction

Soil-structure interaction is one of those interface topics which cannot be treated successfully either as a purely structural problem or as a purely geotechnical problem. A holistic approach is required to the modelling – the identification of the essential details of the problem – and to the subsequent analysis. The geotechnical system in this case is the sum of all the geotechnical and structural elements, and the response of the system will certainly depend on some combination of properties of both the soil and the structure. If the ground and the structure are both behaving elastically, then simple configurations lead to exact analyses. While it has to be admitted that the problems that can be analysed are somewhat idealised, there is sufficient realism to demonstrate and support the important messages of soil-structure interaction.

Let us start with a thought experiment that will seem quite remote from soil-structure interaction. Suppose that we have a quarter kilogram (or half pound) packet of butter (unwrapped) on a plate. We also have a penknife or some other knife with a short, stiff blade, and a palette knife with a rather flexible blade. We place the flat side of the blades of the knives on the block of butter in turn and try to make an impression in the surface. The short, stiff blade will penetrate without difficulty (Fig. 9.1a); the palette knife blade will just bend (Fig. 9.1b).

Summary

Introduction

In this chapter, we introduce the concept of stress and demonstrate how we can calculate stresses in the ground, recalling that we are only concerned with configurations that can be described as one-dimensional. Initial sections rehearse some of the ideas of mechanics – Newton's First Law, the distinction between mass and weight, and the idea of gravity. The single dimension of our problems allows us to impose some notions of symmetry which are helpful in simplifying our calculations of stresses in soils.

We need then to introduce the possible presence of water in the ground. Some background discussion of basic hydrostatics is required in order that we may describe the pressures that exist in the water. We end with a powerful hypothesis about the way in which stresses are shared between the water and the soil.

Equilibrium

Newton's First Law of Motion says that an object will remain in its state of rest or of uniform motion in a straight line unless acted upon by an out-of-balance force. We need not concern ourselves here with the possibility of motion – our soils are expected to be rather stationary or at least to move only very slowly as a result of some construction process. The condition of rest or stasis therefore requires that the forces acting on an object should be in balance.

Summary

Introduction

In Chapter 2 we calculated profiles of vertical stress in the ground on the assumption that we knew the value of the density of each of the several layers of soil. We also noted that soils consist of individual particles packed together in such a way that there will generally be spaces between them – voids – which may contain air or water or a combination of air and water (or other fluid). Knowing the relative proportions of space occupied by solid and liquid and gas, and knowing the densities of the individual components, we can estimate the density of the overall mixture that is the soil.

Density is obviously essential for the calculation of stress, but the mechanical behaviour of soils is also strongly influenced by the way in which the soil particles are packed together. It seems intuitively obvious that the greater the proportion of the volume of a material that is occupied by “nothing” the lower will be the resistance of that material to imposition of loads, so we will need to explore density and packing in parallel. It is unfortunate that soil mechanics has been endowed with a plethora of different ways of describing aspects of the distribution of materials within the mixture – the effectiveness of the packing of the particles – and, although really only two or three of these are necessary (and indeed sufficient) for the presentation and understanding of the response of soils, some familiarity is required with all of them.

Summary

Introduction

Water is a particular source of geotechnical problems (Figs 5.1, 5.2). It is no coincidence that landslides frequently occur during or after periods of heavy rainfall. We introduced some of the basic principles of hydrostatics in Chapter 2 and used the idea of a water table to calculate pore water pressures in the ground and thus convert total stresses (equilibrium) to effective stresses (which control mechanical response of soils). Hydrostatics is of course concerned with water at rest – here we will allow the water to move through the soil (but not very fast) and introduce principles of one-dimensional seepage.

Total head: Bernoulli's equation

There are some basic building blocks that will assist our study of seepage. One is Bernoulli's equation, which describes the steady flow of an incompressible fluid along a streamline, or through a frictionless tube. This is obviously a somewhat idealised situation but the assumption of incompressibility is certainly reasonable for the flow of water under the pressures that are likely to occur in most civil engineering systems. The flow rates in soils will generally be slow.

A reference diagram is shown in Fig. 5.3 for an element of water of density ρw of cross-section A which is flowing vertically with velocity v and with pressures u acting at its base, at level z above some reference datum, and u + δu at its top, at level z + Δz above the same datum.

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Chapter 18 - Genetic issues in introduced and invasive species

Gorgias

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Editorial note

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Introduction

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CAMBRIDGE TEXTS IN THE HISTORY OF POLITICAL THOUGHT

A guide to further reading

Appendix

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Protagoras

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Contents

Principal dates

Index

Frontmatter

Menexenus

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1 - Introduction

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Frontmatter

9 - Soil-structure interaction

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2 - Stress in soils

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3 - Density

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5 - Seepage

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SOIL MECHANICS

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