A small overweight of knowledge is often a sore impediment to the movements of common sense.

An undertaking of great magnitude and importance, the successful accomplishment of which, in so comparatively short a period, notwithstanding the unheard of unestimable difficulties and impediments which had to be encountered and surmounted, in an almost unexplored and uninhabited wilderness … evinced on your part a moral courage and an undaunted spirit and combination of science and management equally exciting our admiration and deserving our praise.
(In recognition of his achievement building the Rideau Canal.)

If physicists could not quote in the text, they would not feel that much was lost with respect to advancement of knowledge of the natural world. If historians could not quote, they would deem it a disastrous impediment to the communication of knowledge about the past. A luxury for physicists, quotation is a necessity for historians, indispensable to historiography.

In my youth scarcely anyone mentioned Wegener’s ideas of a mobile earth and moving continents. … The great impediment was that geologists only studied that one quarter of the earth’s surface not covered by ice or water; at that time no one had any means for exploring the great interior or the ocean floors.

It has hitherto been a serious impediment to the progress of knowledge, that is in investigating the origin or causes of natural productions, recourse has generally been had to the examination, both by experiment and reasoning, of what might be rather than what is. The laws or processes of nature we have every reason to believe invariable. Their results from time to time vary, according to the combinations of influential circumstances; but the process remains the same. Like the poet or the painter, the chemist may, and no doubt often' does, create combinations which nature never produced; and the possibility of such and such processes giving rise to such and such results, is no proof whatever that they were ever in natural operation.

Most impediments to scientific understanding are conceptual locks, not factual lacks. Most difficult to dislodge are those biases that escape our scrutiny because they seem so obviously, even ineluctably, just. We know ourselves best and tend to view other creatures as mirrors of our own constitution and social arrangements. (Aristotle, and nearly two millennia of successors, designated the large bee that leads the swarm as a king.)

The equation of evolution with progress represents our strongest cultural impediment to a proper understanding of this greatest biological revolution in the history of human thought.

The increasing technicality of the terminology employed is also a serious difficulty. It has become necessary to learn an extensive vocabulary before a book in even a limited department of science can be consulted with much profit. This change, of course, has its advantages for the initiated, in securing precision and concisement of statement; but it tends to narrow the field in which an investigator can labour, and it cannot fail to become, in the future, a serious impediment to wide inductive generalisations.

The veneration, wherewith Men are imbued for what they call Nature, has been a discouraging impediment to the Empire of Man over the inferior Creatures of God. For many have not only look’d upon it, as an impossible thing to compass, but as something impious to attempt.

There is no greater impediment to progress in the sciences than the desire to see it take place too quickly.

We do live in a conceptual trough that encourages such yearning for unknown and romanticized greener pastures of other times. The future doesn’t seem promising, if only because we can extrapolate some disquieting present trends in to further deterioration: pollution, nationalism, environmental destruction, and aluminum bats. Therefore, we tend to take refuge in a rose-colored past ... I do not doubt the salutary, even the essential, properties of this curiously adaptive human trait, but we must also record the down side. Legends of past golden ages become impediments when we try to negotiate our current dilemma.

We often think, naïvely, that missing data are the primary impediments to intellectual progress–just find the right facts and all problems will dissipate. But barriers are often deeper and more abstract in thought. We must have access to the right metaphor, not only to the requisite information. Revolutionary thinkers are not, primarily, gatherers of fact s, but weavers of new intellectual structures.