THE FLOATING MAN AND THE METHODOLOGICAL
GROUNDS FOR AVICENNA’S IMMATERIAL SOUL
NICK HALME

While Avicenna is traditionally perceived as advocating for the human soul’s
immaterial nature, his “floating man” thought experiment has been seen to offer
an apparently circular argument. This paper investigates Avicenna’s methodology
in order to contextualize this thought experiment and determine its meaning within
Avicenna’s philosophical system. The paper examines how Avicenna’s conception
of thought experiments and the nature of the soul were influenced by his reception
of Aristotle through the lens of Neoplatonist commentators. The paper then
proposes that this Neoplatonist reception of Aristotle led Avicenna to conceive of
the material and immaterial as logically identical and sharing the attribute of
existence. This paper finds that Avicenna did not conceive of his “floating man”
argument as circular. Rather, Avicenna intended to show that an empirical test of
the immateriality of the soul was possible, providing evidence for his view that the
soul could come into contact with another such immaterial existent: God.

In Avicenna’s Autobiography, he informs the reader that he mastered the 4XU‫ގ‬ƗQ
by the age of ten, and that he quickly mastered the least difficult science: medicine.1
What Avicenna hopes to make clear, besides his confidence, is his view that these
things are not the epitome of the “sciences”—the highest knowledge (al-ҵLOP) being
occupied by philosophy. 2 However, Avicenna had learned from al-)ƗUƗEƯ¶V work
that philosophy could not examine the nature of God, contra al-.LQGƯ and so he
believed that he would have to instead examine the nature of existence in general.3
Avicenna’s philosophy led him to find that the nature of the human soul was not
identical with the material of the body, but was immaterial, and he constructed the
1

Dimitri Gutas, Avicenna and the Aristotelian Tradition (Leiden, Boston: Brill, 2014), 180.
Gutas, 178-179.
3
Peter Adamson, “Al-.LQGƯDQGWKe Reception of Greek Philosophy,” in The Cambridge Companion
to Arabic Philosophy, eds. Peter Adamson and Richard C. Taylor (Cambridge: Cambridge
University Press, 2006), 34.
2

HiPo Vol. 5

15

March 2022

“Floating Man” thought experiment to illustrate his argument. This paper will argue
that Avicenna’s “Floating Man” thought experiment is an intentionally circular
argument, which illuminates the empirical commitments of Avicenna’s
“rationalism.” The paper will first examine Avicenna’s understanding of thought
experiments and introduce the “Floating Man.” Next, the paper will discuss
Avicenna’s Neoplatonist reception of Aristotle. Finally, the paper will discuss the
way in which the circularity of the “Floating Man” is complementary to Avicenna’s
conceptions of “psychology” and the nature of the soul.
The concept of a thought experiment entered the Muslim world through Aristotle,
such that Aristotle’s use of the Greek term for supposition (hupekeito) in the Physics
is mirrored in the Arabic far‫ڲ‬. 4 For Avicenna it was problematic that this exercise
in imagination (fan‫ܒ‬ƗVL\Ɨ) was not constrained so as to ensure such an experiment
usefully reflected what was possible in the world. 5 Although Avicenna inherits from
Aristotle a distaste for the Platonic theory of forms, he constructs something similar
in order to place limits on the imagination. 6 Avicenna posits an “estimative faculty”
he calls wahm with which the mind extracts intentions and, although this faculty is
used to examine mathematical objects in the mind, this same faculty is used to
surmise that a wolf is dangerous because of its intimidating features. 7 It is striking
that Avicenna seeks to limit the imagination with a cognitive faculty which is also
used, without modification, to “estimate” intentions in the empirical realm of
experience.
The general argument of the “Floating Man” is as follows: the reader is asked to
imagine a man who snaps into existence in a void—he is not falling or flying, in
fact he is not in contact with the air at all. 8 His fingers do not touch one another,
nor do his limbs, and he cannot see the world around him. Avicenna then has the
man assess whether his self exists—despite having no knowledge of his own body
or the external world. Despite his predicament, the man is completely sure that his
self, or GKƗW is the only thing the man can detect. 9 Thus, Avicenna appears to have
produced an argument for an immaterial soul which does not require the body—the
implication being that the soul is the sort of thing which could survive the death of
the body.
Marmura considers that Avicenna has committed an error of circular reasoning: to
accept the success of the man’s sensing of his self, one must already accept the
4

Jon McGinnis, “Experimental Thoughts on Thought Experiments in Medieval Islam,” The
Routledge Companion to Thought Experiments, eds. Michael T. Stuart, Yiftach Fehige and James
Robert Brown (London: Routledge, 2017), 78.
5
McGinnis, “Experimental Thoughts,” 79.
6
Gutas, 324.
7
McGinnis, “Experimental Thoughts,” 79-80.
8
McGinnis, “Experimental Thoughts,” 80-81.
9
McGinnis, “Experimental Thoughts,” 81.

HiPo Vol. 5

16

March 2022

conditions required for it to be sensed. 10 When the man considers the absence of
knowledge of his heart or brain as being material sources of the soul, Avicenna is
insisting that the soul to be detected must be immaterial—for a material soul could
not be detected. Marmura argues that Avicenna’s circular reasoning takes the form
of a category mistake: the man’s knowledge of his self—his epistemological state—
is evidence for the man’s ontological state: whether his soul is material or
immaterial rests on what the man knows. If the man does not detect that his brain
or heart are his soul, then they must not be. 11 As Marmura notes, Avicenna
elsewhere presents arguments to establish the nature of the soul—but the “Floating
Man” is not a good argument. However, there is reason to think that Avicenna did
not, in his view, produce an error.
The works of Aristotle with which Avicenna was familiar were, unbeknownst to
him, the product of the “Ammonian synthesis,” the work of a Neoplatonist tradition
of commentators on Aristotle beginning with the eponymous Ammonius in the late
fifth century. 12 These commentators had sought to reconcile Aristotle’s conception
of the soul with a Neoplatonist metaphysics—the belief in an immaterial “formal”
realm which permitted the soul to transcend its residence in the body. Aristotle had
conceived of the soul as entelekheia, or “actuality.” Given Aristotle’s theory of
causation, which designates four types, this suggested that the soul was a formal
cause: the soul “animates” the body—and a material cause: the soul is immanent in
the body. 13 To account for Aristotle’s application elsewhere of entelekheia for
“change,” the Ammonians used the term teleiotes or “endedness” to encompass
both usages, which changed Aristotle’s meaning: the soul was now the final cause
or telos of the body. 14 Aristotle’s formal, material cause was now an efficient and
final cause: the soul produced change in and imparted change to the body. For the
Ammonians this was a relief, as the soul was not the sort of causative agent that
had to remain in the body: it had created the body, and so had existed previously
without it. With this Ammonian influence in mind, Avicenna found it inconceivable
that the soul could be immanent in material, such as an organ.
In On the Rational Soul, Avicenna is explicit about the independence of the
“rational soul” and its transcendence of the body after death. Once a soul has been
separated from the body and has been “purified through knowledge of God,” it
becomes “like a polished mirror upon which are reflected the forms of things as

10

Michael Marmura, “Avicenna’s ‘Flying Man’ in Context,” Monist 69, no. 3 (1986): 387-388.
Marmura, 388, 392-393.
12
Robert Wisnovsky. “Avicenna and the Avicennian Tradition,” The Cambridge Companion to
Arabic Philosophy, eds. Peter Adamson and Richard C. Taylor (Cambridge: Cambridge University
Press, 2006), 96-97.
13
Andrea Falcon, “Aristotle on Causality,” Stanford Encyclopedia of Philosophy, January 11, 2006,
revised March 7, 2019, https://plato.stanford.edu/entries/aristotle-causality/.
14
Wisnovsky, 99-101.
11

HiPo Vol. 5

17

March 2022

they are in themselves.” 15 For Avicenna, the key element of human psychology is
the intellect—that same part of the soul in which the “estimative faculty” resides.16
The intellect contains several parts, but the most vital function is the ability to
conceive of al-ҵLOP—to hold knowledge. 17 The process of obtaining knowledge
requires the intellect to extract from the material world universal concepts.
Immaterial knowledge is necessarily extracted from material and deposited in the
immaterial soul.
Avicenna took al-)ƗUƗEƯ to have meant that God was not the sort of thing that could
be understood, but not that the nature of God could not be investigated. 18 God is
one of the immaterial things which exists; what is problematic is inquiry into His
nature. Avicenna’s explanation of the problem presented by the investigation of
God’s nature is an appeal to Aristotle’s defence of inductive logic in the Posterior
Analytics. 19 Avicenna follows Aristotle in assuming that an inductive syllogism
must proceed from axioms which cannot be understood. For there could be no
acquisition of knowledge if the premises of all arguments were indeed false—the
result would be an infinite regress: circular reasoning. 20 Aristotle simply held that
not all knowledge could be demonstrated. Avicenna concurs—but notes that God is
the creator of all matter and all forms, and as such is like an axiom from which all
knowledge proceeds. 21 Gutas holds that Avicenna came to believe that the world
possessed the same ontological schema as the syllogism—and so a practiced mind
could come into contact immediately with knowledge, without having to “extract”
it. 22 The Prophet is offered as an example of someone who had achieved such a
level of “intellection.” 23 God, the creator of all knowledge, is something that must
be “contacted,” rather than understood. 24 As Avicenna says in his argument for the
existence of God: “no doubt, there is existence.” 25
For Avicenna the self, or GKƗW, is not an object—it is not the soul—it is rather the
effect of all the parts of the soul in action together. 26 This is why the “Floating Man”
is sure that he has detected his self: if the heart or brain were the soul, then the self
would be in “contact” with it. If all that a soul required was a body, it is not clear to

15

Gutas, 289-290.
McGinnis, Avicenna, 123-124.
17
McGinnis, Avicenna, 117-118.
18
McGinnis, Avicenna, 35, 150-151; Gutas, 275, 285-286, 290.
19
McGinnis, Avicenna, 45-48.
20
Aristotle, The Basic Works of Aristotle, ed. Richard McKeon (New York: Modern Library, 2001),
113-114.
21
McGinnis, Avicenna, 150.
22
Gutas, 372.
23
Gutas, 369-372.
24
Gutas, 377.
25
Gutas, 376.
26
McGinnis, Avicenna, 142-143.
16

HiPo Vol. 5

18

March 2022

Avicenna why all bodies—all material things—are not animated and alive. 27
Avicenna’s circular argument is an illustration: the immaterial and the material both
exist, and thus share the same ontological map. Everything which exists is subject
to rational inquiry, except the “axiomatic” Creator. The “Floating Man” is not just
a demonstration which takes place in the imagination; it is an empirical experiment
which demonstrates Avicenna’s philosophical system in a snap. Perhaps this
explains his confidence.

27

McGinnis, Avicenna, 143.

HiPo Vol. 5

19

March 2022

BIBLIOGRAPHY
ARISTOTLE. The Basic Works of Aristotle, edited by Richard McKeon. New York:
Modern Library, 2001.
ADAMSON, PETER. “Al-.LQGƯ and the Reception of Greek Philosophy.” In The
Cambridge Companion to Arabic Philosophy, edited by Peter Adamson
and Richard C. Taylor, 32-71. Cambridge: Cambridge University Press,
2006.
FALCON, ANDREA. “Aristotle on Causality.” Stanford Encyclopedia of
Philosophy. January 11, 2006, revised March 7, 2019.
https://plato.stanford.edu/entries/aristotle-causality/.
GUTAS, DIMITRI. Avicenna and the Aristotelian Tradition. Leiden: Brill, 2014.
MARMURA, MICHAEL. “Avicenna’s ‘Flying Man’ in Context.” Monist 69, no. 3
(1986): 383-385.
MCGINNIS, JON. Avicenna. Oxford: Oxford University Press, 2010.
MCGINNIS, JON. “Experimental Thoughts on Thought Experiments in Medieval
Islam.” The Routledge Companion to Thought Experiments, edited by
Michael T. Stuart, Yiftach Fehige, and James Robert Brown, 77-91.
London: Routledge, 2017.
WISNOVSKY, ROBERT. “Avicenna and the Avicennian Tradition.” In The
Cambridge Companion to Arabic Philosophy, edited by Peter Adamson
and Richard C. Taylor, 92-136. Cambridge: Cambridge University Press,
2006.

HiPo Vol. 5

20

March 2022