Why do some philosophers like Carl Stumpf or Immanuel Kant use the word 'Phenomena', whereas British empiricist philosophers, like Locke and Hume, or even Kant, use the word 'Impressions'?
‘Impressions’ are central to the philosophy of Hume and ‘phenomena’ to that of Kant.
Hume and impressions
The basic building blocks of Hume’s philosophy, at least in the Treatise of Human Nature (1739-40 : ‘T’ hereafter), are ‘perceptions’ – the immediate objects of thought. Perceptions are of two sorts : impressions and ideas. When I look out of the window I see, or seem to myself to see, a tree. This is an example of an impression. In impressions Hume includes ‘all our sensations, passions and emotions, as they make their first appearance in the soul’ (T I.1.1.1 : David Hume, A Treatise of Human nature, ed. D. and M.J. Norton, Oxford : Oxford University Press, 2009 : 7) When I later recall the tree or start to generalise about trees or to distinguish between varieties of them, I am using my idea of a tree. Ideas are (a) causally dependent on impressions (no impression, no idea) and (b) are less forceful and lively than impressions, of which they are the ‘faint images’.
Hume subdivides impressions : there are impressions of sensation and impressions of reflection. The latter, we are told, ‘are derived in a great measure from our ideas’ (T I.1.2.1 : Norton & Norton, 11).
It sometimes happens that an idea, which in its turn is derived from some precedent impression, will "return upon the soul" (p. 8) to produce new impressions, of pride, humility, ambition, vanity, hope, fear, desire, aversion, or any of the countless ‘passions and other emotions resembling them’ (R.P Wolff, ‘Hume's Theory of Mental Activity’, The Philosophical Review, Vol. 69, No. 3 (Jul., 1960), pp. 289-310 : 290).
Hume professes ignorance about the origin of impressions of sensation, which are more fundamental than those of reflection. They occur ‘in the soul originally, from unknown causes’ : ‘without any introduction [they] make their appearance in the soul’. It is not merely the case in my view that Hume is personally ignorant of the origins of impressions of sensation. The problem is deeper :
As to those impressions, which arise from the senses, their ultimate cause is, in my opinion perfectly inexplicable by human reason, and ’twill always be impossible to decide with certainty, whether they arise immediately from the object, or are produc’d by the creative power of the mind, or are deriv’d from the author of our being. Nor is such a question any way material to our present purpose. We may draw inferences from the coherence of our perceptions, whether they be true or false; whether they represent nature justly, or be mere illusions of the senses. ( T I.3.5.2 : Norton & Norton, 59.)
Hume, then, is concerned with impressions of sensations as objects of thought, not as representations of the external world.
In this respect like Locke, Hume rejects innate ideas; our ideas derive from impressions and our impressions of sensation arise we know not how. But Hume concedes that we have no impression of time, space, causal connection, necessity, universality or of an external world independent of what we seem to see. I cannot literally perceive time or causal connections. Yet I have ideas of these things. How is this possible ? Hume attempts, what many regard as an impossible task and as revealing the philosophical bankruptcy of empiricism, to derive these ideas by abstraction from our impressions. We have, for example, impressions of sight and touch and the imagination (a deus ex machina) integrates these impressions into a compound impression from which we abstract the idea of space. A quite basic problem is that if we have no corresponding impressions, how do we know what to ‘abstract’ in order to derive the ideas of (say) space, time, and necessity ? If we don’t know what these things are from impressions, how do we light by abstraction on ideas of them ? How do we know what to abstract ?
This marks a key point before we move on to Kant. Hume’s impressions time, space, causal connection, or of an external world independent of what we seem to see, and only by ‘working on’ our impressions can we derive abstract ideas such as those of time, space, causal connection, necessity or of an external world independent of what we seem to see. Much as I admire Hume, I think he has set himself an impossible task here. Others may disagree. I can only present my own view based on the texts as I understand them.
Kant and phenomena
It is a very different picture with which Kant presents us. Hume starts from the bottom up, Kant proceeds from the top down. That is to say that Hume starts with atomistic, discrete, unorganised impressions and tries to create a world of experience in which we operate with ideas of time, space, causal connection, necessity and the rest derived from these impressions. Imagination and abstraction are called in aid to deliver the requisite ideas. Kant’s view is rather that experience – Humean impressions, if you will – tells us only that things are thus and so but not that they are so by necessity or are universally so. We do not abstract these ideas or concepts from experience. On the contrary, experience is possible only on condition that we apply these concepts a priori to experience. What Hume regards as experience delivered through impressions of sense would be an unintelligible jumble, nothing coherent at all, unless certain a priori concepts were brought into relation with what Kant calls ‘the manifold of sense’. There is some input from some kind of externality but we never do or can identify it separately or determine its nature. We only ever experience this input inextricably interpenetrated with the a priori concepts which are our contribution to the possibility and nature of experience and knowledge.
What I have loosely called ‘a priori concepts’ need much closer and more refined treatment than I can offer here but I believe the following elaboration is essentially correct.
We can, Kant argues in the Transcendental Aesthetic of the Critique of Pure Reason (1781, 2nd ed. 1787 : Kant, Critique of Pure Reason, tr. P. Guyer & A. Wood, Cambridge : CUP, 1998, 172-92), perceive objects, or have sensory experience, only under the forms of space and time or ‘Forms of Intuition’ as Kant calls them). These forms belong to the mind, to the human cognitive apparatus, and not to the matter – the input – provided to the mind. Further, what we receive from whatever externality there is can be converted into objects of experience only by means of categories, which again are a priori. They are Quantity (Unity, Plurality, Totality), Quality (Reality, Negation, Limitation), Relation (Substance and Accident, Cause and Effect, Action and Reaction) and Modality (Possibility and Impossibility, Existence and Non-Existence, and Necessity and Contingency). Only via these categories, set out in the Transcendental Analytic) can objects of experience be thought at all. (Kant, Critique of Pure Reason, tr. P. Guyer & A. Wood, Cambridge : CUP, 1998 : 204-44.)
We do not self-consciously apply the Forms of Intuition (of space and time) or the categories. They are inherent in the way in which we experience objects.
All this, so far, has centred on the conditions that make knowledge possible. But what of the limits of knowledge ? Here we encounter phenomena, and the phenomenal world. If the objects of experience are inherently penetrated by the Forms of Intuition and the categories, we have no way of knowing what reality – ultimate reality – is like independently of how we ‘process’ our input by means of those Forms and those categories. We would have to perceive reality independently of how we process it in experience, and perceive it as we process it, in order to determine any difference. But it is impossible to make the comparison because reality independently of how we process it in experience is inherently impossible for us to perceive. Our knowledge is confined, in Kant’s terminology, to the phenomenal world – the world of experience structured by the Forms of Intuition and the categories. The noumenal world is reality as not given in sense perception and incapable of being so given. This allows the possibility of a more positive notion of the noumenal as knowable non-perceptually by intellectual intuition or, as may be, in moral experience. But these matters lie beyond my remit.
A Treatise of Human Nature: Edited by David Fate Norton and Mary Norton (Oxford Philosophical Texts Series) David Hume ISBN 10: 0198751729 / ISBN 13: 9780198751724 Published by Oxford University Press, 2004/ 2009.
The Cambridge Companion to Hume, ed. D.F. Norton, ISBN 10: 0521387108 / ISBN 13: 9780521387101 Published by Cambridge University Press, Cambridge, 1993 : 6-12.
R.P Wolff, ‘Hume's Theory of Mental Activity’, The Philosophical Review, Vol. 69, No. 3 (Jul., 1960), pp. 289-310.
Critique of Pure Reason (The Cambridge Edition of the Works of Immanuel Kant in Translation) Immanuel Kant; Editor-Paul Guyer; Editor-Allen W. Wood ISBN 10: 0521657296 / ISBN 13: 9780521657297 Published by Cambridge University Press, 1999/ 2009.