What does Descartes mean when he uses the words "thought", and "doubt", in Cogito ergo sum.

Could you please give me possible interpretations and definitions of the words.

As the argument progresses, one would naturally assume that he meant two different things when he referred to those two words, and then finally assumes that "doubt" is a subset of "thought".

My real question is at what point did he assert that "doubt" is a subset of "thought"? Before he begins "Cogito", or after he has established his method of deduction, which is to doubt all that there is in the world.

Or did the order of the arguments not matter to him at all.

Wikipedia says this on Cogito ergo sum:

Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us; And because some men err in reasoning, and fall into Paralogisms, even on the simplest matters of Geometry, I, convinced that I was as open to error as any other, rejected as false all the reasonings I had hitherto taken for Demonstrations; And finally, when I considered that the very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep, while there is at that time not one of them true, I supposed that all the objects (presentations) that had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams.

It's clear from this, that Descartes allows himself to be the ultimate doubter, doubting everything that enters his mind.

Throughout my writings I have made it clear that my method imitates that of the architect. When an architect wants to build a house which is stable on ground where there is a sandy topsoil over underlying rock, or clay, or some other firm base, he begins by digging out a set of trenches from which he removes the sand, and anything resting on or mixed in with the sand, so that he can lay his foundations on firm soil. In the same way, I began by taking everything that was doubtful and throwing it out, like sand.


Descartes's method for seeking out knowledge. The Cogito has to be based on it. So, clearly Descartes intends to seek out the indubitable, but by first throwing out all that is doubtful, by applying doubt to all.

  • 1
    Two thoughts. There have been quite a few questions on this at this SE. First, did you look to see if any of those contain the information you seek? Second, Descartes gives a list of the operations of the mental faculty in Meditation 2 itself: "But what then am I? A thing which thinks. What is a thing which thinks? It is a thing which doubts, understands, [conceives], affirms, denies, wills, refuses, which also imagines and feels."
    – virmaior
    Nov 9, 2017 at 0:14
  • Is this after he has established the cogito or before? I understand the cogito, but wished to know ALL the possible interpretations of those words, or definitions if there are any. @virmaior Edited my question as well.
    – novice
    Nov 9, 2017 at 0:16
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    Before he begins "Cogito", or after he has established his method of deduction, which is to doubt all that there is in the world. seems to be a very poor understanding of his method. First, cogito is what we call his argument. Second, his method of deduction is most assuredly not "to doubt all that there is in the world." At most this lasts a page in a 50 page book. (have you read his Meditations and/or Discourse on Method?)
    – virmaior
    Nov 9, 2017 at 5:23
  • 1
    Again, no really, he doesn't go about "doubting everything in the world." This occurs only briefly at the beginning before he abandons that as implausible. The "cogito" in its briefest form happens several lines above what I quoted above.
    – virmaior
    Nov 9, 2017 at 6:23
  • 1
    Please, read the second meditation yourself. In the Methods, he explicitely refers to the Meditations, so that should be your starting place. It's only few pages to read, really.
    – Philip Klöcking
    Nov 9, 2017 at 18:28

1 Answer 1


See Descartes' Theory of Ideas:

According to Descartes’ ontology there are substances, attributes, and modes. These are understood relative to one another, in terms of ontological dependence. Modes depend on attributes, and attributes depend on substances. The dependence relation is transitive; thus, modes depend ultimately on substances. No substances, no modes. [...] Attributes are in fact what make existing substances intelligible to the human mind. [...] This strongly suggests that although one may draw a conceptual distinction between an attribute and existing substance, the two are not distinct in reality. They are really one and the same thing.

The nature of a mind, Descartes says, is to think [emphasis added]. If a thing does not think, it is not a mind. In terms of his ontology, the mind is an existing (finite) substance, and thought or thinking is its attribute. Insofar as the nature of a mind is to think, where thought is the mind’s defining feature, Descartes calls it the mind’s principal attribute (AT VIIIA 25). An idea is a mode of thinking.

This is similar to what Descartes says about a body, its principal attribute, and its modes. The nature of a body is to be extended (in length, breadth, and depth). A body is a (finite) substance, and extension is its attribute. Since extension is the defining feature of a body, Descartes refers to it as a body’s principal attribute. Shape is a mode of extension. What this means is that shape is a way of being extended, or a way in which an instance of extension is manifested. Thus, shape is to extension as idea is to thought.

  • Thank you! If I claimed that Descartes did not consider the order of statements when he made the Cogito, would my claim be true?
    – novice
    Nov 9, 2017 at 15:25
  • Is Doubt another attribute, as far as Descartes is concerned? Could you also please give me an example of a mode in the answer?
    – novice
    Nov 9, 2017 at 15:35

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