I do not suggest that piecemeal engineering cannot be bold, or that it must be confined to ‘smallish’ problems. But I think that the degree of complication which we can tackle is governed by the degree of our experience gained in conscious and systematic piecemeal engineering. [ch. 9, n3]
The difference between Utopian and piecemeal engineering turns out, in practice, to be a difference not so much in scale and scope as in caution and in preparedness for unavoidable surprises. … [W]hile the piecemeal engineer can attack his problem with an open mind as to the scope of the reform, the holist cannot do this; for he has decided beforehand that a complete reconstruction is possible and necessary. 
We should be thankful for every serious attempt to criticize our positions. Praise is of no intellectual value. Victories in debates are of no intellectual value. Yet if we can succeed even in getting a little clearer about our problems, we should be very happy with that intellectual achievement. 
Every reputable political or social policy is a proposed solution to a problem; and we always need to be clear about the problem before we can propose the solution. We must always be able to ask of a policy: “To what problem is this the solution?” If there is no problem to which a given policy is a solution then the policy is superfluous, and therefore harmful, if only because it consumes resources to no purpose. … The whole notion that you can start with policies is deeply erroneous, and very damaging in practice. 
First of all, we are required to formulate our problems with care. That means, among other things, not taking for granted what they are. We have to ask ourselves what precisely are, say, the main problems that face us in the field of primary education? What, precisely, are the main problems that face us with the treatment of teenage offenders against the law? What, precisely, are the main problems that face us in our relations with the United States? And so on and so forth.
There will, legitimately, be differences of opinion about what the problems are, before one has even begun to think in terms of solutions, and these differences should be thoroughly debated. It is of the utmost importance to get diagnosis right before one proceeds to cure, otherwise the proposed cure will be the wrong one, not effective, quite possibly harmful. So a lot of time and trouble and thought and work needs to go into the identification and formulation of problems before one attempts to move forward from that position. …
[P]roposed solutions need to be critically examined and debated, with the explicit object of bringing their faults to light before they are turned into reality. 
I am a democratic socialist and I believe that the young Popper worked out, as no one else has ever done, what the philosophical foundations of democratic socialism should be. And like him I would like to see these ideas replace the garbled mixture of Marxism and liberal-minded opportunism which passes for politcal theory on the demoracric left: in 1962 I published a book advocating this in the context of British Labour Party politics called The New Radicalism. In short, while making it clear that Popper is no longer a socialist, I want to claim his ideas for the democratic socialism in which he was so deeply enmeshed when he began to produce them, and in response to whose needs they were produced. This is where I believe their real significance is, and where their future lies. My longest-running argument with the older Popper is about what in my contention is his failure to accept, in matters of practical politics, the radical consequences of his own ideas.
The guiding principle for public policy put forward in The Open Society is: ‘Minimize avoidable suffering’. Characteristically, this has the immediate effect of drawing attention to problems. 
Das Wichtige am Entwurf einer mittelfristigen Perspektive innerhalb politischer Strukturen ist, daß er formell auf den legitimen Entscheidungsprozeß bezogen sein und zugleich von den Anliegen entfernt sein muß, die den Horizont der Entscheidungsträger begrenzen. Sie muß, mit anderen Worten, eine gesetzliche Grundlage haben, aber unabhängig sein in dem Sinn, daß die Amtszeit der Beteiligten länger ist als die von den Regierungen und Parlamenten. Um das zu erreichen, lassen sich verschiedene Wege denken. Einer ist ein Amt für technologische Bewertung, um einen irreführenden, aber anerkannten Begriff zu verwenden: eine Behörde, in der Sozial- und Naturwissenschaftler regelmäßig die Politik der Regierung angesichts erklärter Ziele und bekannter Entwicklungen überprüfen. „Technologie“ bedeutet in diesem Zusammenhang die Übersetzung von Theorien in Praxis und die Bewertung der Praxis im Licht der Theorie. Möglicherweise könnte eine solche Einrichtung von der Erfahrung des deutschen Sachverständigenrates für die gesamtwirtschaftliche Entwicklung profitieren, dessen Jahresberichte einen erheblichen Einfluß auf die Wirtschaftsentwicklung des Landes haben. Ein gesetzlich verankerter Rat für mittelfristige Planung, der der Regierung jährlich Bericht erstattet, wäre eine Methode, um eine Mehrzahl von Erfahrungen zu verbinden. Auch auf andere Weise ließe sich wohl mit dem gleichen Problem fertigwerden: daß diejenigen, die sich vor der Öffentlichkeit für das verantworten müssen, was sie gestern getan haben und heute tun, nicht vergessen, daß es auch ein Morgen und Übermorgen geben wird. [110-11]
What is the characteristic difference between a scientific theory and a work of fiction? It is not, I hold, that the theory is possibly true while the descriptions in the story are not true, although truth and falsity have something to do with it. The difference is, I suggest, is that the theory and the story are embedded in different critical traditions. They are meant to be judged by quite different traditional standards (even though these standards might have something in common.)
What characterizes the theory is that it is offered as a solution to a scientific problem; that is, either a problem that has arisen before, in the critical discussion of earlier tentative theories, or (perhaps) a problem that discovered by the author of the theory now being offered, but being discovered within the realm of the problems and solutions belonging to the scientific tradition. 
Popper (1972, 107-108) presents one of his “standard arguments for the independent existence of the third world” with the help of a thought experiment. Compare the following two situations: (a) All our machines and tools are destroyed, and all our knowledge of them. But books and our capacity to learn from them survive; and (b) all our machines and tools are destroyed, and all our knowledge of them. All books are destroyed, too.
In the second case, Popper argues, it would take much more time for the world to reemerge. I think that this hypothesis is quite plausible. Let us assume it is true. What follows from this? According to Popper (1972, 108), his thought experiment demonstrates the “reality, significance, and degree of autonomy of the third world.”
This, however, does not follow from the premises of the thought experiment. Strictly speaking, this thought experiment only demonstrates the significance of books. We may conclude that books, at least some of them, are significant things, which could, under special conditions, decisively influence how the world goes on. If we presuppose, in addition, that books are world 3 objects, then it follows that some world 3 objects are significant things. But the thought experiment itself does not tell us that there is a world 3, and that books are world 3 objects. Books could have great impact yet be physical things. After all, physical things can also significantly change the world, and our life (e.g., the impact of a meteorite).
Popper further illustrates the reality and influence of world 3 by referring to problem situations in science and mathematics. As an example, he presents Brouwer’s invention of his theory of the continuum. He cites the following statement by Heyting about Brouwer’s invention: “If recursive functions had been invented before, Brouwer would perhaps not have formed the notion of a choice sequence” (Popper 1972, 109).
The details of this example do not matter. The example illustrates the point in question. Quite plausibly, problem situations may greatly influence the thinking of scientists. But here, too, we have to distinguish between two questions. The first is whether problem situations exert an influence on world 2, and perhaps on world 1. It is quite another question what problem situations are ontologically. They might be world 3 objects, but they might also belong to worlds 1 or 2. Popper’s example teaches us nothing about this question. It only illustrates the impact of problem situations, not their ontological character. 
Among the inmates of my ‘third world’ [World 3] are, more especially, theoretical systems; but inmates just as important are problems and problem situations. And I will argue that the most important inmates of this world are critical arguments, and what may be called—in analogy to a physical state or to a state of consciousness—the state of a discussion or the state of a critical argument; and, of course, the contents of journals, books and libraries. …
Let me repeat one of my standard arguments for the (more or less) independent existence of the third world [World 3].
I consider two thought experiments:
Experiment (1). All our machines and tools are destroyed, and all our subjective learning, including our subjective knowledge of machines and tools, and how to use them. But libraries and our capacity to learn from them survive. Clearly, after much suffering, our world may get going again.
Experiment (2). As before, machines and tools are destroyed, and our subjective learning, including our subjective knowledge of machines and tools, and how to use them. But this time, all libraries are destroyed also, so that our capacity to learn from books becomes useless.
If you think about these two experiments, the reality, significance, and degree of autonomy of the third world [World 3] (as well as its effects on the second and first worlds [Worlds 2 and 1]) may perhaps become a little clearer to you. For in the second case, there will be no re-emergence of our civilization for many millenia. [107-8]